Never had much in the way of a PH problem before but today a couple of my fish tanks looked glum so checked PH and it was like very low fairly close to 6.0 never been like ever before so i buffered it and is better now. the tap runs 7.5ish and was wonder what i need to look for in the tanks that would drop it so much. The tank i have a lot of drift wood in is fine 7.0 and the other do not have drift wood in them. thanks