Jarren -- never dose without test kits. This is why I've been telling you for months you need your own test kits -- if you're blindly 'treating' the chances of you fixing the problem are next to zero, whereas your chances of introducing new problems are very high. Magnesium, Calcium, and Alkalinity are all directly tied, and too much of a shift in any of them can cause the dreaded precipitous event.... Go get yourself some test kits, the SeaChem sets are nice and affordable, and reliable enough. If you wanna really be serious, get some Elos or Salifert test kits ;)

Definitely looks like Bryopsis without a closer pic though -- manual removal during water changes will help on top of testing your own water and fixing the imbalances properly...

-Corruption