I had a female mandarin dragonet in a very well establish tank. She pretty much had the same thing going on as far as signs go. I had her for over 2 1/2 years. She died a few days later, but mine would also eat frozen and lived brine shrimp as well. I would bring them home and soak them in socon over night and feed them next day. So food was not the factor there, I did notice her color was getting lighter and she wasn't moving around as much. At the same time I also notice that my six line wrasse was picking on her. I think stress played a big roll on mine with her changes. I only mention this because stress may be a factor on your as well. Why, what, where and who it may be coming from.
Right after she died, guess who was taken out the tank. Yeah the wrasse, he took out two wrasse before her as they jumped out the tank because of his harassment but when he did that to her, he was out for sure. She was my favorite fish at the time. Right now due to not having any fish eating my cope pods, I seem to have an infestation going on. I need another mandarin as soon as I get my new refugium sump up and running and has been established for a few months and I'll add a cope pod breeding station to make sure they keep replenishing into the main tank. You may want to try this as well and add a cope pod breeder.
