is it threadworm?

Hello we have a Ocellaris Clownfish we have been having what we think is a thread worm problem. i have been doing a freshwater dip and the "threadworm" falls off and got another one the next day. he looks perfectly heathy so i thought it was just poo but if let go it will stay on him all day. i don't have any pictures of it right now but if it comes back i will take a picture.

Tank
75g sw
405 fuval. polishing pads top, Biomax next, Carbon next two media trays
80 degrees f
8.0ph
1.023 gravity 32 salinity
nitrite is 0.2 nitrate 2.5
ammonia 0.5
tank has been up for 3 weeks yes it was rushed
about 60lbs of live sand
17 or so lbs of lace rock and 3 lbs of dead coral
we have:
2 Ocellaris Clowns
1 bi-color
1 dragon goby
1 yellow tail damsel in qt right now for color fade and a ripped up fin we had two but they wouldn't leave each other alone now i have a hurt fish and a dead one i am treating the live one with quickcure and freshwater dip.

I know we have alot of fish in the tank only after 3 weeks. the tank hasn't cycled yet this whole thing was rushed. I am not very happy about it i would have liked to put in LR and let it cycle with no livestock but i have no control over it so I'm doing my best to try and keep it going. Thanks for any advice.