First wattering + Feeding

The entire pot must be moistened so that the entire potting soil is moist, but not soaked. Normally we say that on a good watering, 10% of the water you give should end up in the cup under the pot. Then you have to wait for the first 4 to 5 centimeters of potting soil to dry before watering them again. When they are really small, you have to water every day around the plant so that the soil on the surface remains moist. Its roots are not large enough to draw water from deep. 😉

Normal procedure: 1) always water with fertilizer and never partially get the pot wet - always 10% runoff waste water. 2) wait for top layer to dry 3) repeat. keep it simple. A light dose frtilizer in the first 7-10 days is fine, but you'll quickly want to use a full 1.3-1.5 EC well-balanced mix including everything a plant needs. Even 'full' dose will not cause issues with a seedling unless some component is way out of balance. Your VPD and what comes in your tap water will influence exactly what a 'well-balanced' diet is for your garden. high vpd = lower concentration. Lower vpd = higher concenration needed compared to normal. simple relationship. tap often comes with Ca, Mg and even a little N at times. maybe some S? Unless you have very hard water, shouldn't be too big of an influence though. Anyone telling you a specific volume of water is wrong. You give what is necesary to get the job done. How your substrate is constituted will determine how much is needed as well as the amount of dryback you allow to occur -- if you repeat at same loss of weight, then it will require the same volume of water. So, you can predict it, but you cannot choose the volume whimsically. Now, because you followed the urban myth that you shouldn't "transplant" an autoflower, you have complicated the entire thing. You have to (partially) water an increasingly larger circle around your tiny plant as it grows, but you still want to make sure it gets wet all the way down or you are training roots to grow superficially, otherwise. It will remain wet for long periods of time because your plant can't drink much. This is less than optimal. You still want to try to wait as best you can form 'some' dry back before re-irrigating. you still want to water all the way down to bottom. As long as the circle of what you water increases, should avoid/minimize any potential buildup of nutes in the areas with ebb/flow of moisture depositing nutes that will go into solution 'next' time and potentially build up. Just one of the drawbacks of not transplanting. Water at least as wide as the current canopy. If you could see a cross-section of the substrate, you'd see it will form a cone-like shape of moisture... fatter at bottom where gravity pulls it and more time to absorb into sorrounding substrate. roots turn toward moisture, if you don't water all the way down, you'll get more superficial roots. superficial roots are not optimal. With a soilless medium you should have a well-balanced fertilization formula and feed every irrigation - 1.3-1.5EC, well-balanced will do well. Always get 10% runoff or more to reset equilibrium of nutes in substrate. Small adjustments do not require a "flush." Simply adjust formula based on plant growth/symptoms and carry on. The runoff will change it almost immediately. Larger adjustments maybe jump to 20% runoff to hasten that process. Why you should transplant autoflowers: https://www.cocoforcannabis.com/transplanting-cannabis-plants-why-when-how/ the negatives of a big pot and small plant far outweigh whatever perceived benefit there is from avoiding a transplant that will never shock your plant if you have half a brain while doing it. this is one of those things that get repeated until everyone believes it. I've yet to see transplant shock 1 time out of hundreds of transplants, albeit some are not autoflowers, but that is irrelevant. it's no less robust of a weed.

Shes looking good. I would be closer to 6.5. tds is okay. That is plenty of water for the plant but may need a little more to prevent dry pockets. It is good that you have extended your watering to 7 days. Theirs a good chance that the roots are bigger than you think right now, so you want to kee getting the water deep to get the roots to grow down more.I would water until you notice it is the right weight or a little bit of run off indicating you have the medium fully wetted.

Soil volume determines the amount of water, not the plant. Usually it is around 5-15% or soil volume as water, depending on the type of substrate. Most of the times it will be around 10% of the volume in substrate with soil like properties. Water slowly and if needed in multiple portions until you get a little runoff and the substrate is heavy. Let the top layer of substrate dry out / wait until pots are noticeably lighter in weight & repeat the process. Always water with 10-20% of runoff on coco with salt based nutrients. Coco doesnt hold as much water as peat for example and doesnt provide any nutrients/doesnt hold nutrients very well, so water and feed regularly (feed a little bit with every watering) Good luck!