URGENT: angel lost fin

[clown jr]

we got a juvenile french angelfish and a while after it came home, couple of weeks ( he had been fine ) he got white stuff on a fin. the lfs said its prob cauliflower and it should go away. we left it and now HE LOST HIS FIN. the yellow tang and coral beauty are in there helpin him but hes been layin on the ground. PLEASE HELP!!!

 

[clown jr]

please help anybody... all suggestions appreciated

 

[clown jr]

i always heard lympho shouldnt kill em.... does it cause em to lose the fin its affected???
and hes layin cuz he cant swim well missing his fin.. we put him in a quarantine bowl at the top of our tank ( i know, not real qt but all we could do last minute w/o setup for qt, its just a tupperware keepin him out of strong current, other fish territory, etc... )
what can i do?