I had the same problem when I was doing DWC. I was always chasing the ph when the plats started drinking a lot of water. I think its caused by the plants drinking more water than nutrients so it would change your ph and your ppm of the reservoir. I had to keep adding water and either ph up or down to correct it. I"m also battling some spider mites right now. I tried the No pest strips and they would go away for a while but keep coming back even though IO left out the strips. Now I just said screw it and ordered the predator mites. There only $30 for 500 spider mite predators. I bought 2 of the strips and they were 410 a piece plus your not supposed to use them in the last 2-3 weeks of flower. Other than that nice grow... can't wait to see some nice fat nugs