My yellow watchmen goby has been in my tank for over a year now, and the past 2-3 weeks he hasn't come out as much and I havnt seen him eat. Today I saw him for the first time in about 6 days. I had feared the worst that he had passed away and his pistol shrimp partner had eaten his corpse. But today I saw him come out, he looked skinnier then normal with dark bands around him and some white patches. Along with some either white mucus or sand in its mouth. (Videos of him below) I'm currently going to try and catch him and put him into the QT tank to monitor him more closely. Any advice or knowledge would be greatly appreciated!