Blackberry NFT

Looks like perhaps old over water damage sort of. If new growth is coming out green and healthy with no droop or curl, then your good, and i would pick off the damaged leaves as they are vulnerable to pathogens now. Never mist your plant leaves either. Do you? Water left on the leaves can magnify the light and cause leaves to burn.

Really hard to diagnose. At first i was sure it was lack of iron, but iron deficient plants usually start to yellow from leaf stem to tip. Yours are yellowing tip to stem. Nitrogen defecient leaves usuallu yellow from tip to stem but they typically yellow evenly without leaving any green leaf veins. And the yellow tends to eventually crisp up, turn brown and die. Your leaves are yellowing tip to stem, leaving green leaf veins. What most closely resembles what i see your leaves doing, based on my research, is Sulphur deficiency. Here is a link for you to explore that i think will help. https://www.zamnesia.com/grow-weed/499-sulphur-deficiency-cannabis-plants

I had a look at your latest week. Ya if I had to guess i would say increase the nutrients. If it's a lack of nutrients you'll see a leaf from the tip in start to go a paler green and will move through the leaf down to the stem. The plant is pulling nitrogen out to give it to new growth.. your TDS is 450. You should be at 750 to 800 at this stage, if you are starting week 3 of veg that is. Monitor your pH daily cuz it can fluctuate. 5.8 for hydro is ideal in veg. Looking a second and third time at your plants, too me, my best guess, is that your pH is out of range. You have necrotic spots on some lower leaves. Your growth tips are extremely pale. If i remember correctly that is a sign of iron deficiency. You also have raised leaf edges on some of the leaves. Sometimes early magnesium deficiency shows that way. Raised edges could also be low humidity. When you mix your nutrients, always mix in your micro first, then grow, then bloom, but always micro first. And pH your water after you've mixed your nutrients. If you mix your water to 5.8 and then stir in your nutes, the nutrients usually drop my pH by a full point. And, when you add your ph down, add it slowly. Like 20 drops at a time then stir and test....etc. If you dump a bunch of pH down into your nutrient mix you might see it look cloudy when it moves through the water. Thats bad! Thats your nutrients becoming bound to each other and getting locked out. Pick off the damaged bottom leaves on the runt. The damage makes the plant vulnerable to pathogens and disease. Pick up some General Hydroponics Calimagic. Nitrogen takes a ride on Calcium ions I believe. A last ditch effort if upping the TDS and keeping a close eye on the pH doesn't net any results, is drain out your res and mix a fresh batch on nutrients the way i mentioned above. Frankly i'd just flush and re-do your rez. Last edit i promise. After doing some looking around and a bit of research, i can tell you that the yellowing at the tops is not lack of nitrogen, it is a IRON deficiency. The way to spot that is that iron deficiency always displays at the tops of the plant. Nitrogen is a somewhat uniform yellowing of the entire leaf. Here's the difference. Your plants growth tops are yellowing but the veins of the leaves remain green. You need to get some Cal-Mag because not only does it contain calcium and magnesium, but it also contains some extra iron. Iron is most available to plants grown hydroponically between a pH of 4.0 to 6.0. Anything above or below those ranges and iron is unavailable to the plant. Try to keep your pH consistently around 5.8. Get yourself some cal-mag and adjust your pH to 5.8 and try to keep it there and they will green up again.