I'm not anything close to an expert...I'm on my first hydro grow, but I'll still throw in my 2 cents lol.

First, if I understand correctly, you've got 9 plants in a 3 gallon bubbler? I've got 6 plants in a 13 gallon DWC system and I've had people tell my that my res is too small for that many plants. Maybe they're too crowded in there? Not sure on this tho. It's just a thought.

Second, if these are in full veg, 300ppm is probably too low. I've got mine running at 600ppm using the Lucas Formula and the plants are loving it. Also, check your res temps. Even if your pH is right, if the res temps are too hot, the plants can't eat. Same with room temps.

Last you've definitely got a nute imbalance somewhere in there. I'm not good enough to tell you exactly what, but if you post in the sick plant forum, there's a guy named Ganja Guerrilla who's really good at figuring out what nutes you're missing, just by looking at your pics.

P.S. The Lucas Formula is a really simply nute program designed specifically for weed. I switched to it in my second week of growth and I'm really glad I did so.
Help_Needed Reviewed by Help_Needed on . I'm trying to defy the odds...but My friend found some really good "dro" there was a couple of seeds in it,she decided to throw them in some dirt,a week later she was amazed because they started to grow,She gave me 3 plants,one died.I grew hydro before and I noticed a very fast growth rate compared to soil,I took the plants out of the dirt and I transplanted them to my bubbler,in the meantime I sprouted 7 other seeds that I had.Now I have nine plants in a 3 gallon bubbler(the plants that she gave me are about 4 weeks,my Rating: 5