If your pH continues to be low, and you have corals in your tank, your growth rates for your hard corals will be greatly diminished. At lower pH it is much harder for the coral to precipitate the calcium carbonate from the water in order to incorporate it into there skeleton. I would seriously consider adding a kalkwasser drip or dosing by some other means. In addition, low pH can have negative effects on marine fish including decreased reproductive success. I'm sure Brad from GCreef could chime in and tell you more about the effects on marine fish.