sometimes cats find somewhere else to havekittens rather than home , a few years ago my pregnant cat came through the catflap looking skinny (panick stations) shed got in through a broken window in my shed , which was overloaded and bursting , took me about an hour and a half in the dark with a torch to unload shed and find the kittens in the farthest corner , i was lucky it was in my back garden but could of been anywhere i keep outdoor cats in a week before due date now but as misty is going to be done in a few weeks and all my other cats are house cats shouldnt have that again ................ and i guess as much as we'd like to think our cats are good mums it also takes alot of effort to ensure the kittens are kept clean safe and healthy , changeing bedding , fleaing and worming introducing litter and food so you can understand how a ferral litter of kittens would look so bad , i expect mummy cat has been doing her best but its hard work in the wild so thankfully you have rescued these babies and will bring them back to good health ........................ good luck wirh them !!!!!!!!!!!!!!