Oh no! Hopefully if you start treating asap with Protozin or whatever, you might be able to prevent any fish deaths. I hope so.
Also, where you were saying you didn't want to upset the peace in your tank by the Convicts spawning - I think you'll find that Severums and Convicts have very similar breeding pattern/behaviour. They will become very territorial at spawning time, and continually chase any other fish away from their side of the tank. I found that all out when doing research on Severums and was also warned by the LFS of this (remember, they sold me the fish as Severums). Actually I think a lot of cichlids behave in much the same manner, from what I've read up on. So, if you're intending on having a pair of severums be prepared for some tank wars when they start spawning LOL

. Might be best to leave Goldie on his own, perhaps..
Anyway, all the best with tackling the white spot!
Athena