ph problems

Good day everyone. Im a beginner at all this and seem to be having a hard time maintaining the proper ph levels...
im in my second week from sprout and the first full set of leaves are starting to spot. brownish/yellowish... burnt almost, starting at the tips.
the water s ph in the res. will rise within a matter of hours. I thought it was because of the water temp? and maybe stagnant water?.. So in the res. i put in a airstone and a heater to 75* but still rose rapidly.
6 gal. of water
2 part rockwool formula 1/2 strength
top fed drip system
4 in. airstone
50w reservoir heater
6 40w 4ft. fluros.
4 in. rockwool cubes in ? size containers filled with hydroton clay pebbles
...will the nutes constantly react in the res. affecting the ph?
it has to be the ph affecting these guys. Can anyone tell me how to maintain a constant ph level? Thanks a bunch

The yellowing of the leafs you explain would be a N deficient trait. What type of nutes are you using and of what strength? You shouldn't have a water heater unless you see temps below 55 degrees IMO. Cold water stays fresh and crud free longer it maintained properly. How are the roots looking?

rastajbd said:

The yellowing of the leafs you explain would be a N deficient trait. What type of nutes are you using and of what strength? You shouldn't have a water heater unless you see temps below 55 degrees IMO. Cold water stays fresh and crud free longer it maintained properly. How are the roots looking?

Click to expand...

Im using Rockwool Formula 1 (8-6-11). I just bumped up to full strength per recommended directions for early growth. when i transfered the cubes to pots 3 days ago the roots were very healthy and white.
I have a 6 week old as well that ive been using as sort of an experiment. this is the reason i believe it to be the ph since i eliminated all other factors.
my water in the res. looks cloudy after only one day of feeding and smells a little as well.
is this normal?
Are my rockwool cubes contaminating my res after i presoaked them before use?
the hydroton grow rocks are a neutral ph.
i dont have a digital ph meter but have a drip kit and color chart to follow.
im guessing at exact numbers but i get the water to about 5.8 and 6.2.
next day it looks to be about 7.5 ....wtf!