PH rising too much-too fast

[savique]

Strain- Royal Dwarf (autoflowering) 2plants
growing-Hydro
grow stage-veg in around 18 days from seeds
light-120watt LED
nutes-Advanced nutrients
RH-35-60%
temp-73-79
ec

I am first time grower and i have a big big problem with the PH adjusting.In first i use distiled water and now i use tap water.The ph of my water is around 7.7. I use GHE ph down/ph buffer solution. I down my ph in 5.5 and then just after 1-2 hours is 6.8 its going up.In last week i have use many things for better result such a citric acid but the things its going the same.Also the ec of my solution its going up i left at night in 0.65 and in the morning was 0.80.I run the hydro system 24/24.I have done some experiments with stopping it for a feww hours and the ph its not going up so fast.Any thoughts for my prob???? soon i upload some pics for better info.

MANY thanks....

 

[sanjose]

i had the same problem what i did was fill up a 20 gal bucket with tap water get the ph down to 5.8 it is going to rise fast but just leave the water out over night but cover it so you dont get dirt in it the the next day re test the ph and adjust it to 5.8 and it should only rise one time for the first day but then it stays pretty stable i couldnt figure out another way i am sure there is another way but this worked for me so mybe it will work for you
good luck