I'm not sure of this, but I would not go much below 5.5-6 with your flush water... I think it could stress the plants... not certain though.
stinkyattic Reviewed by stinkyattic on . PH Lockout ? Here are a couple of pics. My friend has been taking care of them for a few weeks and this is what happened. They are in FFOF with about 40% perlite. I flushed them with 5 gallons each of 7.0 ph plain (tap unfortunately) water tonight and the runoff was between 7.3 and 7.5. They have been getting half doses of Thrive alive, Grow Big, and Liquid Karma at 2/3 of their waterings (the other waterings are plain water). The first two pics are Sour Diesel and the others are blueberry and they are Rating: 5