That sounds more like mold. With aluminum reels, it's tough to see the white powdery stuff on the outside of the tape pack. Also, if it was sticky shed, you probably would've heard some squealing, on longer tapes in particular. 3M tapes are very prone to SSS but if the stuff that was on your tape guides and heads cleaned off easily, it's probably mold.
The big problem with mold is the spores. This can spread the mold to other tapes in your collection. Hopefully you didn't fast wind any of the tapes because that will distribute the spores throughout the room (and adjacent rooms if there was a breeze). Of course, spores are everywhere unless you use a good air filter and unless you're the curator of a large collection of priceless tapes, you should be able to minimize any cross contamination pretty easily. You need to clean your entire machine and the immediate area around it with damp cloths changing them often. Let that dry and then vacuum an even larger area. Hydrogen peroxide will kill most spores but I'm not so sure how it will affect the finish. I think if you're very thorough with your vacuuming, you should be OK. Throwing the contaminated tapes out is a good idea but take the reels apart and clean them very well before you reuse them.
Like I said, mold can be a major problem in an archival/restoration facility, but for the casual user, a good cleaning should do the job.