Possible fin rot?

[ajwetton]

My powder dwarf gourami seems to have tail fin missing I've never seen fin rot in a tank wondering what to look for,

20 gal tank

Kept 78-80 degrees
Ammonia was up to a 1 last night I've been doin water changes for it and adding prime.
0 nitrites
10 nitrates
Recently lost 2 guppies but I think that was due to forgetting prime on a water change 2 days ago like an idiot.

Any help would be appreciated I can try to post a pic later I'm at work ATM.

Edit: just attached a pic of his back fin.

 

[Matt68005]

looks like it might be too late. Have you seen white stuff on the tail before tonight? I would lower the temp a bit maybe and just withold food for a couple days and Keep water clean. Is the tank cycled? Melafix or primifax (or both) might help in this case.

 

[ajwetton]

I wasn't aware of cycling when I got the tank and have been doing daily water changes to keep levels down while I try to fish in cycle. I didn't notice anything odd except his tail diminishing, no white or anything just shrinking tail size.