The only plant I find suspicious is the first one. The one with curled and hard leaves looks more like too wet /too much fertilizer damage.

i.

So the first one might have signs of mites? That is one of the plants with the hard somewhat curled-under leaves...however the center leaves seem to be folding on each other and having trouble pushing past each other.

http://i1068.photobucket.com/albums/u441/Ceropegia00/IMG_0133.jpg

This plant is quite underpotted and probably the soil got old. When it gets old, it gets acid and dense, so the amount of air goes down, amnount of water goes up. I would wash the old soil off to some extent and repot it.
For me - it looks more like a culture issue. But what do I know - I am familiar with cyclamen mite damage - and it doesn't look like it. But there are broad mites and who knows what else.

The idea is that the language of the plants is limited - and they react the same way to different negative things.

Mites spread like a forest fire and the damage is seen real fast. If you have several plants touching - and they do not go to pot at the same time - it is not it.

I.