I have been having an ongoing problem with my guppy tank. I had 10 guppies in my ten gallon, and one by one, they have been showing the same symptoms. First, they get a kinda brown rot on their tails, and their tails begin to clamp a tad. Then, their spines bend, and make them appear 'cresty' almost. Then, their tails clamp fully, and they swim around and eat normally for a few days, then sink to the bottom, unable to get up, at which point I have been removing them and putting them down. I have just put down two more fish, and moved the five healthy ones to a sterilite bin makeshift quarantine tank. My ten gallon is so nicely cycled, I don't want to completely tear it down unless I have to. On a couple fish, the scales have stuck out, and on some, they have gotten extremely thin. But what baffles me, is that the entire time they swim around and eat. I have toyed with the idea of internal parasites, and fish TB. Please help!