Answer

The skin problem sounds like ringworm to me. Ringworm is a fungus, and it is common in the environment and is very contagious. Other possibilities include mange and ear mites. Ringworm and some forms of mange are contagious to humans. If these cats are not wild, then you should take one of them in to the vet to be tested and find out what the problem is.

Here is info on ringworm: http://www.marvistavet.com/html/ringworm.html

The deaths are most likely not related to the skin problem, but I can't say this for sure, as I have not examined or tested any of these cats for disease. If you want to find out why they are dying, you will need to do a necropsy on one of the deceased cats. The next time one passes away, very quickly get the body to the nearest vet school or vet clinic that can do the necropsy (this is an autopsy on animals). You may find out what is causing their deaths this way.

Best wishes