PH Problems

This is my first hydro grow and my question is probably going to sound pretty noobie... My ph changes every day and since its my first grow i dont know if this is normal.. i have 3 plants and a 50L res. I am using regular tap water, AN sensi 2 part, supertrive,and h2o2. Is this normal or is there something wrong with my mix of chems?

your rez temps are wayyyy to high.

Check for root rot ... infected water makes ph go nuts

I put in cold tap water yesterday and set the heating blanket to high to heat up the res... smoked one too many joints and forgot to lower it... but this was happening before the temps were high... it was actually worse when i was using distilled water and someone recommended tap water because its more stable supposedly? whats the ideal res temp?

Roots seem fine... nice bright white .. no signs of root rot that i can see.