Oh Jan noooooo. I'm sorry to say but this does not sound good at all.
I hope and pray that you got these babies to the vets in time and they pull through and especially that none of your own cats have come in contact with it.
Oh Jan, my heart is aching for you. You must be a basket case right now. I know I would be.
I wish I had some encouraging words for you.

Also, wouldn't the vet had known this could be FCV by their symptoms or do they have to be tested for it?