Not testing alk is the main problem. I'm surprised you have been getting away with it for so long. Yes, GFO can reduce your alk, so that also is not in your favor. Over use of GFO can also result in tissue loss. Personally, I would not raise it without first having it tested. If it is indeed low, don't try to raise it more than a point a day throughout the course of a day, not all at one time. How often are you changing the GFO, and how much? I would take it offline until you get the problems addressed. You need RODI water. Just because you got away with it it the past, doesn't mean it's OK. Your corals are in a weakened state, so you will have to deal with pests and infection after your parameters are back in line.