not good. this is exactly why ALL new reptiles should be quarantined for a minimun of 90 days. that way you can catch any issues with the new animal before it is introduced to your animals, enabling the problem to spread.

knowing that they are losing weight and fluids your best option may be to have them euthanized if the test results are positive for crypto. i'd take them all in to your vet and have her assess the situation. she should be able to advise you the best course of action.

i'm sorry this has happened to your geckos. how long ago was it that you added the newest gecko? you may still be able to get some kind of recourse from the seller if this was a recent purchase.