PH goes down daliy, big issue!!!!!

hI GUYS,

IM FACING SOMETHING THAT IS HAPPENING FOR 2TH TIME, THE ph GOES EVERYDAY FROM 6.2 TO 5 AND OF COURE THE PLANTS ARE GETTING BAD.
BUY THE WAY IM GOING NFT WITH HISE NUTRIENTS.

GIVE SOM HELP GUYS PLS

my water did same but mine went from 5.5 to 8.0 just keep puting it up cover the container as much as possible and it should find it self after a while but untill it does u might av to live with doing it everytime u wanna feed but ph at 5 aint that bad u only wanna av it around 5 to 6