79F is not good at all. You need to be ideally at 65F. I don’t think using anything like Hydroguard would make a difference at that temp. Invest in a chiller.
Questions:
Are you running air stones and how much air? Rez too?
How far below net basket is rez? It should be 2" or so below.
Why are you still top-feeding? Have the roots not reached the rez? Once they do, discontinue top feeding.
PH is a bit high and I’d prefer to see it at 5.7 or so.
When did you last calibrate your PH meter?
I don’t use that nutrient line but do know that some products are optimized for different types of water i.e. GH is meant to be used with R/O and FF in 200 ppm tap water. Mixing different lines can cause trouble (as I found out using FF cal mag instead of GH). You want something buffered for your PH range to be truly useful for RDWC.