Stunted plants - Any solution left?

It is probably genetics. But also pot size. They look too big for those pots. The yellowing of the lower leaves is a good sign that they may want more space. a good rule of thumb is that if the top of the plant is bigger than the pot or reaches the edge of the pot then the roots probably are becoming root bound. Transplant into something bigger and maybe flower if youre not happy with the genetics and tight internode

You need to put them in bigger pots and just let them explode, The tight spacing and dense growth are a sign she is vigorous and wants to grow, but is stifled in those little pots. The hard part is getting them out of those things, normally id use pots that roots can grow through for initial seedling stage, cork cardboard or coco, then its just as easy as popping small pot in bigger pot, you want to dry out the pots as much as you can, the dryer they are the easier they will transplant. Leaves are wrinkled, drooping, and transpiration is low; given that transpiration is the driver of nutrient uptake, you will need to rule out environmental factors or saturated/compressed soil first before considering a nutrient deficiency. hard to give an accurate cause, but with so many visual things going on, I would not be surprised if it's pH-related. Get them in better-sized aerated pots, be fabric or airpots, and remove the possibility of overwatering, people don't think of oxygen as a nutrient in itself but due to its relatively weak bond it is and if it isn't readily available in the medium when its most needed then this will slow things down a lot or even cause problems if left unchecked. Photosynthesis drives Transpiration, the more water the plant needs for this process, the more water it pulls up through the medium via the roots.. As gas is exchanged through the stomata, more pressure is created. IT IS this pressure that dictates how fast water will cycle through the plant, it is also the counter pressure used by roots to push through compressed or difficult mediums. Adequate oxygen in the soil is a requirement for transpiration to happen, and if it's limited, so too will be the transpiration rate. Roots need oxygen to respire and function properly, and this, in turn, impacts transpiration rates. What drives photosynthesis is not the same as what drives transpiration, because transpiration deals with water from both the medium and water in the air, if any end of the water cycle is not optimized or RH% is too high, the stomata will close. Transpiration by the day, water is pulled from the soil Cellular respiration by night (Zero transpiration), no water leaves the pot unless evaporation occurs. In a perfect indoor world, you want to water once in the morning, 15-30 minutes before lights on, by the time nightycycle approaches, the soil is perfectly moist, not too dry, not too wet, at night respiration occurs and that takes oxygen from the air and spits back out the moisture, no moisture from soil is used. Leaf will transpire 3x@86F what it will at 68F, little extra airflow daytime, lots of oxygen hitting those pots. There is bottlenecks, your plants are sucking up far more water than they can release through the rate of transpiration, either bad watering habits, High RH, saturated soil, lack of oxygen to perform rooot respiration if waters not moving on one end or the other for any reason, waters not leaving those platics, especially if no evaporation occurs (0 in plastic pots) nutrient salts are not moving, salts will build, ph will skew, water will stagnate. Bigger pots, fabric or air, temps up a little, rh down a little, constant gentle airflow. If you insist on plastic pots, I'd recommend increasing the pore space in medium to at least 40% of the medium or up to 55% at most to optimize (use more than just perlite) will go a long way to help alleviate soil compression and compaction. Like separate gears on the same engine, the different factors must be in balance with each other. This comes through understanding the different mechanisms at play on a day/night cycle Lots of good answers, hope you get things worked out!

You should be able to keep those plants in those pots for a week or 2 for them to recover don’t try and transplant when they are already so stressed that will make them be super stunted

To small a pot, over watering and possibly to strong a light. 2 growers have given good answers on watering techniques and pot sizes.

Hey there over watering is 100% the stunted growth let the soil get really dry it’s ok if it takes 10 to 14 days with small plants in those pots Also with node spacing you just have to lower the light intensity I give seedling me like 70par to start then around 100 or so until there getting close to the size of your plants they will be a little more spaced out and then when plants are just a little smaller than yours I start giving my plants 200 to 225 umol’s/ par When you see those ppl that have plants that are all short and didn’t strech out at all it’s cause they blasted there plants with light from seedlings Also lowering light intensity will give the plant some vigor the plant is used to what light you have been giveing so when you give less it will be able to not be stressed at all and Start to space out a little bit Also keep in mind every grow light and environment is different. Like in my 2x2 tent I have just a 100w light and in that tent when I give plants 200umols it’s not enough I have to give like 225 to 240 but in my 2x4 tent I have a 500w light and when I have plants your size I only give them 200umols under that light… idk how to quite explain it but side lighting makes a big factor in things aswell like my 100w light is only like 14in wide so even with 1 plant under the light the light is only going directly down on the plant but in my 2x4 the light is pretty much as wide as the tent it’s almost 4 feet wide so the plants in the tent are getting light fron directly above but also for angles from the parts of the light not directly over the plant So just experiment some with lowing light intensity and see how the plants react…. Keep in mind when you lower light intensity it will take about 7days until the plant starts to grow in a pattern reflecting that lower light… plants like to plan for the future so if it’s been getting more light lately its internal clock is planing for that amount of light and will grow for a few days with that plan but by a week later it will have changed up what it wants todo there like on a 3day lag

4.7 litre pots are waaay too small............20 litre pots are much better. Tiny pots with cramped roots will limit growth. Other than transplanting, there really isn't a whole lot that you can do, but at 4 weeks for autos, flowering won't be far off.

Your plants are stunted mainly because of early salt buildup and acidic substrate, not light stress. Starting nutrients too soon on unknown soil without runoff testing led to extreme EC levels (4+), blocking root function. The low pH (5.4–5.8) made it worse. Light intensity played a small role, but the real problem started at the roots. Right now, don’t feed anymore – just give light, pH-balanced water (6.2–6.5) and only when the pots feel light. Keep lights around 60–70% to avoid extra stress.