Cage,
long time no chat ? mate sounds like you have a swim bladder problem, never really had any luck treating them unfortunately. As for the slime sounds, like you need a good anti biotic to fix them up, just go easy before you throw everything in there,melafix,prazi,salt mate you will stress them out to much with too many medications, mate just keep doing heaps of w/c get the temp up a little and they should be ok, sounds like they got the discus flu !
cheers