Going back to your first post, you say that you have to adjust the Ph every other day. For your Ph to be rising this much within a day seems to be the issue. Just from my experience, which is growing DWC exclusively for over a decade now. When ever I have had plants that start to look like yours it's always the Ph being too high. When corrected they take off and look great. With me I had been using a dodgy Ph meter for too long and would give me false readings. It would be only when they started to look like yours I would re check Ph and see that it was too high.
When in Veg, as they drink slower, I can have plants sit in a reservoir for over a week and the Ph doesn't change at all. To be having to re adjust Ph a whole 1.0 every other day is a problem. Also when I've had minor root rot issues it was usually from being sat in a too high Ph reservoir for extended periods or too high temp water, however you say the temps are fine. Something is making your Ph increase far too quickly, don't have an answer for you but maybe try to dial back whats going into the res to just the 2-part nutrients. Then see if Ph still increases as fast, then add the extra suppliments one at a time and check to see if you can see if its one of the suppliments causing this.
Im just reading about these nutes now and they say they have something called Ph perfect. Which they say automatically adjust Ph to be correct. To be honest I'm not sure how much I trust this and could quite easily be the cause of the Ph increase. Any one with anymore info on this Ph perfect system might be able to help as it sounds a bit odd to not have to check your Ph in DWC. Lots of issues normally arise from the PH going over 6.0 in regular DWC grows.