My PH is crazy

I am running a flood and drain system and about to start the flush. My nutrient solution is supposed to stay around 5.6. Every morning I set it to around 5.6 and the by the next morning the solution is about 6.3. I have gone through a bottle and a half in 7 of PH down in 7 weeks just to keep it right. I thought this was normal until I was told that was very unusual. Does anyone know why my PH raises so fast.

How big is your reservoir? A smaller res allows for greater Ph drift. Also, what nutrients are you using? Are you adjusting your Ph after you mix your nutrients? Temperature can also affect Ph as well. How are you oxygenating your water in between cycles? Not enough oxygen in the water can cause it to go stagnant and affect your Ph levels as well.

Also, if you are growing in hydroton, did you wash them off first?

I washed off the hydroton before I put them in there. I use advanced nutrients and adjust the PH after mixing weekly. The temperature is very high however, usually around 84 to 85 degrees.

this is bound to happen, its mostly happens because of your plants feeding, the more nutes they take out of the water the higher the ph goes

if you notice when you start out clones on feeding they ph goes up very very slowerly after it has normilized. Basically the bigger your plants or more mature, the more nutes they wil eat therefore rendering you with ph going up

You need to do something about those res temps. The higher the temps, the less dissolved oxygen the water can hold. This is bad for your plants. Additionally, higher res temps can lead to pythium (root rot) and other nasties.

what do you suggest a good res temp be at?

Generally accepted "good" res temps would be 65-72 degrees give or take a degree or two. If it possible, you should keep your reservoir outside of the grow room. If this isn't possible, there are steps you can take such as insulating your reservoir, or if you have the extra cash, you can pick up a chiller for $200 to $300.

So 65 degrees wont mess with the roots, 65 degrees is chilly to the touch, being that the human temp is 98 (around there)

Nope, 65 is good. Lot's of dissolved oxygen in that water, which is good for roots