Urgent Starfish is DISINTEGRATING!

WOW... I've not had this happen before!
My little red sea star is disintegrating, LITERALLY, leg by leg. It started with two of its legs, at the tips, and I thought something got to it. BUT, it has been on the glass this entire time, and now FOUR legs are "melting away"! Does anyone know why this could be happening? This little guy has been with me for several months, and no problems yet. My other starfish (orange sea star, brittle star and Fromia marble star, all much larger than this one) are fine so far.
I know they're sensitive to changes in water chemistry, and the last time I tested my perams, they were perfect. But, it's been almost two weeks since I tested, with a fresh water top off and 10% water change in between. Another question: How often should I be testing? I haven't done a test in a while because I needed a new test kit, which I just bought. I will test when I get home from work, but at this rate, the star won't survive that long. It just started disintegrating last evening, and now it's so much worse.

I posted a pic, sorry about the poor quality, but this is what it looked like about 2-1/2 hours ago. Any help would be appreciated, and thanks!

 

It's probably starving and won't make it. Starfish seem to be so hit ot miss. Oh, and that thing will probably release a bunch of toxins into the tank so i'd give him a flush before it gets too bad.

 

BUMMER... but how on EARTH can he be starving if I feed the tank twice a day- once with either a "coral mix" or mysis, and once with either phyto feast or zoo feast? I have a red sea fan in this tank too, and it needs to be fed frequently to survive. Also, I've had this sea star longer than any others, 5-6 months, and he's been fine up until now.

 

what are "perfect" tank parameters? also, a lot can change in two weeks. if there's something going wrong in your tank the first thing you should do is test your levels and not assume nothing has changed in two weeks. generally speaking one should try to test and dose once a week. i usually test the day after i do a water change

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