It's been a long day. I re-read your post and know what you will be using for nutes after all. I just can't tell you what to expect in the way of PH changes.

Be sure you read the nute labels carefully before mixing. With the GH 3part, you must mix the micro 1st or, from my understanding, you will get nute lockout. I don't know that this is fact, it's just what I've read and I haven't tested for verification.