Well I read your 1st post again and I can say...You should add airstones to your rez for more oxygen.

What kind of medium are you growing in.
usually ebb and flow growers water 15 minutes on every 2 hours.

Your whole problem could be the medium and the water schedule. Get back to me, I'll try to help.
latewood Reviewed by latewood on . HYDRO PROBLEM, HEEEELP!!!!!!! System: Hydroponic, ebb and flow, 40 liters tapp wather. Nutrients canna substra flores. Day temp 26-28 Celzius. Nitgh temp 22-24 C. PH 5,7-6,1. Nutrient temp 22-23 C. Humidity 55-60 %. Ligth 400 hps. EC tryed 1,6-2,0. After 4 days of flowering the problem acured. I thougth it was a nutrient burn, so I took EC down to 1,3 - 1,6 , that did not help. Using magnesium (epson salt). EC of the pure wather is 0,06. Wathering every hour for 5 min, have a sirculating pump in solution. Problem acure Rating: 5