Orange Linkia--looks in trouble


New member
I have had an orange linkia for about 6 months, and it had been doing great.

It now looks like is has blisters on the ends of its legs, and one of them has ruptured. Still moving around OK, and I haven't seen anything pick on it.

Any suggestions?
Salinity should be fine. 1.025 and stable. I use a calibrated refractometer, and the salinity hasn't changed. I have an auto-top-off, so it shouldn't even swing measurably with evaporation.
I have not been able to keep a linckia alive for more than a year and a half. I've had 2 blue and 2 orange, and I won't get any more. They seem to do great for a while, then go downhill. I don't know why, but I'm not sentencing any more of them to death in my tank. I can't deal with it.