I’m confused mate. The autopot res is non active. By that I mean the plants don’t actually drink from it. It flows into a separate smaller res from which they absorb everything so why is the res ph changing? Got an air stone it in it? Even a wee 4w one will keep it all fresh as a daisy. Get a soil probe and test pots properly too. If you putting through 6gal and it’s still coming out higher than your putting in it’ll be well off. Wouldn’t raise the feed either.That’s as high as anyone ever needs to go. Common cause for bad ph in the pot is the nutes being too strong. They build up as the plant isn’t absorbing everything and can lock each other out. Always best to keep feeds as light as you can without bits turning yellow in order to avoid that.