Well ease up on the vodka to start. That can cause problems if not dosed right. The amount of vodka has to be slowly raised and you need to be religious about dosing it other wise you can see rtn and other problems, I switched from dosing vodka to warner marine ecobak ulns biopellets, I have tried other brands but I like the ecobak best. Biopellets are nice because they do the same thing as vodka but you just set them and forget them until they are gone, then you add more. Also test your magnesium and make sure its around 1300ppm. Another thing could be flow, if your lps are getting too much flow the flesh can start to peel away. Give you a few places to start anyways and if you can get some pics posted that would help us to get a better idea of what might be going on. Its kinda like trying to help someone fix a car over the phone its hard to see what could be the problem.