When I got my betta Archimedes he had finrot and his tail was pretty short as a result. I treated with melafix, the finrot cleared and he has had some tail regrowth in the past months.
Recently I noticed that his tail is looking rather straggly. I'm not sure whether this is due to bits going missing from his tail, or due to regrowth that is uneven (he's always had a slightly messy tail since the finrot).

Anyway, in the past week I gave him a mirror and watched him flare, and twice I saw a tiny bit of red stuff fall from his tail (which I can only asume is part of his tail). The pieces were about 1mm by 1mm. He's not got any dark bits on his tail (like he did when he had finrot). But I'm a bit worried.

Here's some pics.
http://img.photobucket.com/albums/v280/lak342/tail2.jpg

just the end of his tail
http://img.photobucket.com/albums/v280/lak342/onlytail.jpg

http://img.photobucket.com/albums/v280/lak342/tail.jpg

http://img.photobucket.com/albums/v280/lak342/mybetta.jpg

This pic is off when I first got him. You can see the black edges his tail where he had finrot and you can see his tail is shorter than it is now

http://img.photobucket.com/albums/v280/lak342/bettabowl.jpg

he can still have the early stages of fin rot or a chronic case of fin rot without the tail being reddened. I had an elderly betta who did. Actually his tail would improve with bettafix ( melafix) salt and added heat.Then as soon as I would stop the salt and Bettafix ( I kept the heater going) his tail would get bad again. Turned out as long as I kept the bettafix and salt going with the heat his tail continued to improve. But as soon as I would stop one of the three his tail would detriorate again.