could be healing spots, as you mentioned black specks earlier, posibility of hosting burns. You see that a lot when clowns host in carpets.
White stringy turds are definately signs of Brooklynella, but you would need symptons of heavy breathing and scrathing too.
If you can find it, look for a product called ImmunaVital, not sure which LFS out there would have it, but Big Al's might. It will help strengthen the clown's immune system.
Like ColdFX for fish.
Ken - BWA