Dude if your runoff is 6.8 and your going in is 7 youre golden! I am a HUGE PH guy and if I had what you have going on I wouldn't fuck with it at all, maybe shoot for the 6.6 range but anything from 6.3-6.8 and you are good! I do 7.0 all the time with water and shoot for 6.6 with nutes before I feed PH. Now that you have PH down move onto something else you need to get done, just never forget to PH your water. IF you get lazy and feed with say a PH of 5 or 8 you will do ireversable damage to your girls just because you wanted to save a few min! Not worth it when you have 30 plants!