Usually when someone asks if you are using carbon, it means if you are not then you should be due to the detrimental effects you are witnessing. Are you using a filter sock or filter pads at the moment? If not, it would not be a bad idea to use one for the time being to catch any organics just as long as you change/wash them frequently. If neosporin is the only outside "chemical" introduced into your tank, then I do not believe that is the culprit. You have other corals that will react much more rapidly/negatively if a harmful "chemical" was introduced and if this was the case you would have an overall tank decline. As far as the coral mixing is concerned, more than likely the mushrooms were not stung, but my point was that you have corals with the potential to sting at great distances so be careful during placement. As far as you have seen, your galaxea has 5in. sweepers, but there are other determinants as to why the extension could extend to 14in+. The Euphyllia you have, whichever sp., also has the potential to produce long sweepers; although, not quite that of galaxea nor as potent not to mention there is the possibility of chemical warfare within the confines of your little glass box to which you would not visually notice until a coral is affected. More than likely, at this point in time, the Euphyllia sp. is recessing because of the protozoan infection your mushrooms succumbed to, their defensive mucusing, and the eventual die off residues. If you can include a clear pic of "froggy" that would help determine if the coral is just closing up as a defense, actual tissue recession, or possible infection setting in.