To me it looks like mold...

do you have any fans blowing on those babies? Air flow helps prevent mold and such like that

I'm not sure what's to be done about it now though. I'm sure there is some sort of additive that will kill it or maybe just some nice air flow will take it away.

Don't take my word on that last part though, let the experts help on that part. I would just say get some air flow on them stat and that will not only provide a nice constant air flow, but it will help strengthen the stems of those pupps too.

Hope everything clears up!!!