Time to switch Nutes

Well. im about to start my 4th grow. the first 3 have been with AN 3part. each of my 3 grows around week 4-5 flowering plants show brown spots/yellowing on leaves. im pretty sure its cal/mag issues. If i wanted a nutrient line that is stable with PH like the AN products what would i look for? any help would be nice. FYI i do have a 60dollar PH meter and can adjust PH.. i just havent ever with AN cause there NUTES made my 3gal DWC sit 5.7 and would peak at around 6.1 3days later....

I'm about to throw all my AN products away and find a whole new system. I've been hearing a lot about some nutrient line that has the word greenhouse In it but I have no idea what the other part is. Anyone who has any idea what brand or website I'm talking about please help me out.