You may be able to salvage some if your willing to open the floppy shell, and gently clean the disk surface with isopropyl. You can sometimes pry/cut the halves apart without major damage.
I did this years ago to some very dusty disks and it worked on most of them. I also cleaned the inner cushion with compressed air.
Could be a combo of damp (winter) and heat (summer). I think heat is the real killer.
