what type of ph reader are you using.elec readers need buffered every 5 days.and need new electrode evry 3 months.always keep reader with wet tipand not dry.i find liquid readers better than electro reader.you av 2 check ph every 3 to 4 days.ph down dont go off it acid and keeps for some time but dont leave in your grow room.as heat can spoil da content .remember to leave water for about an hour before rechecking ph level.let me know if this any help.gman corby town uk...peace