Blue stuff? I have lots of blue medicines... Nox ich is blue, (for velvet and ich, which none of those match) and methelyene blue..
It sounds like whatever it is may be contagious -- do not use the same containers/buckts/hoses/nets on the healthy and unhealthy tanks -- that can make it spread.I would keep a contaiminated water bucket and a non-contaiminated water bucket for changes if you have tanks large enough to need buckets.
I'd also wash your hands very very well before handling different fish houses -- that is all i can really suggest to try to keep it from spreading.
I don't really know what to tell you to solve it -- I would check the bottles of the medicines you are looking at to see if the symptoms match what you are dealing with. I swear by Jungles, nox ich and meth. blue for most of my fishie treatments -- and a little bit of good old fashioned aquarium salt for my betta houses.
Have you added any salt to the tank? Maybe it'll help a little bit. Salt basically helps to promote healing.
I really wish you luck. Your poor babies!