is the 195-200 reading PPM since your expressing in KH? if so that roughly 11dkh or 4 Meq/L. those #s are getting close to being too high. I would guess your Mg is a little on the low side and some precipitation as a result of this imbalance is cause a reduction in Oxygen in your tank which in turn will affect your ph,, use the online calculater in the do it yourself forum if you want to dose a bit of baking soda to help with the Ph, but regular water changes, some extra water aggitation at the surface and maybe the addition of some magnesium should help solve your ph problem.