Hrmm. Sounds like theres an awful lot going on in that tank, and not necessarily in a good way *sigh*
If theres any small white dots (about the size of salt) then you have ich in the tank. If they are really tiny dots and the fish kinda look like they were dusted with talc or golddust, then it might be velvet. You also most likely have some sort of bacterial infection as evidenced by that really bad fin rot. And there may even be a THIRD prob; that thingie coming out of the zebra's side may be a diff parasite. My guess is the zebras are REALLY stressed by the johanni, and are coming down with everything as a result. You really may want to consider separating the zebras and the johanni; it does not seem to be a working combination.
There also another issue which complicates things. Higher temps (above 86f) is usually an effective treatment for ich (I use temps around 88f); thing is, you don't want to raise temps with a bacterial infection (understand this is NOT verified and is word of mouth; the thought behind it is it causes the infection to spread more quickly). Ugh. What a mess.
I would do a couple of things. Keep the temps where you normally keep them. Get a broad spectrum antibiotic to treat the infections. Quick Cure (and I think RidIch) will treat velvet and ich, but I'd be sure thats whats going on before using them. Take a peek here to see if anything matches: http://www.fishpalace.org/Disease.html
. Do know your bacterial colonies will most likely keel over with any of the meds needed for treating; normally I'd say pull the obviously sick fish and QT them, but if the problem is ich or velvet you'll need to treat the entire tank.
Do check that website, confirm whats going on with your fish (obviously everything I have said are guesses once removed from what your actually experiencing) and keep us updated in case we can help.