All of my kittens seem to have developed some sort of skin disease. Some of them have these little bumps that break when you scratch them. I have posted the link to some pictures, if anyone has information regarding this disease, then please enlighten me. Kitten pics
Your cats have most likely ringworm. This is an fungal infection in the skin of your cat. To be sure take a look at each of the bald spots and see if they have a thin dark line around them. This can be hard to see if the skin of your cat is dark.
It can be several other skin problems too. You can take a look here https://pets.webmd.com/cats/ss/slideshow-skin-problems-in-cats and take a look at the pictures.
You will need to take your cats to the vet to get it diagnosed and treated.
It might take months before you see any improvement after the treatment have started so be patient.