ph Fluctuation Like Crazy Help

i am running house and garden aqua flakes A and B and all additives wich i have used in the past and the ph was always very stable. now every time the lights come back on the PH plummits to about 5.2 or 5.3. i am going throught PH up quickly every morning i dont get it, ill PH back o about 5.7 or 5.8 and by the next day its back to 5.2

could it have something to do with running an airstone in the res i never ran it in there in my previous grows