What kind of water r u using. I find now that I use RO water to start my ph stays super stable. I’m using Megacrop 2 part the new sweet candy mammoth p and slf 100. I ph up with tnb naturals and the solution can sit in res for days and stay 5.8. That’s where I set it that’s where it stays. I thought with the microbes and all the stuff in the sweet candy it would drift one way or another but it stays set. Res is looking clean for the most part quick wipe down in between grows most it’ll need. Gonna get a big syringe and flush lines with hot water in between grows as well. This is my first run so I have no idea how dirty or clean the lines r. Hoping the slf100 is doing what I paid it to do.