Dispars are not as hardy as lyretail or bartlett. Sometimes they do fine, sometimes they never adapt...refusing food. I currently have one in my tank. Nowhere near as gluttonous as lyretail, pinksquare, redbar, bartlett or any other hardy anthias that I have kept before.
Eaten away tails could be from either aggression from the others, or a bacterial infection, or both. IME, anthias don't get parasites like ich too easily, but they are susceptible to bacterial infection (sores, red areas, and the like).