Thanks all, but Im too late. Got home Friday and went to feed the tank, the seahorse looked aweful. Laboured breathing, and all looked fine aside from white patches and super sluggish behavior, which is weird because this was the much more spunky one, full of P&V the day prior. Would not eat, and it wasnt more than a couple of hours until she was gone.
Tank params were fine, 0 across the board, PH at 8.2-8.3, temp at a stable 75. Did a WC few days prior as well (weekly 20%). No previous signs of anything wrong. The night prior it was fine, and eating well.
The sad part now is I have a lonely only left in the tank. Not sure if it is going back to the LFS or if we may find a mate.
It occured to me that this horse may have been stung from your description.
Do you have any dangerous tank mates in this tank, such as stinging corals? If so they need to be removed immediately to protect the remaining seahorse.
The only thing in the tank are star polyps, a kenya tree, and 2 dead gargonians (bought them dead for perching). CUC consists of a few hermits, assorted snails, a brittle star, and of course: bristleworms.
Im still reading up on what it may have been with no luck. The only thought I have now is if there is something contagious in there.
It's also really handy to have a small quarantine tank set up where you can transfer sick individuals for treatment immediately they show signs of stress. It can be as simple as a 5 gal tank with a hitching post and a sponge filter in it. It's been my experience that unless you take action immediately the seahorse shows signs of discomfort (like the second missed feed) it's hard to bring them back from the edge. Sorry to hear you lost your seahorse.