Hi and welcome to YT
. Congrats on your new little ones!
Okay...on the skin issues - you do need to get to the vet ASAP bc something is definitely going on here if both of them are itching at the same time this badly -- this could be mange/mites and if it's that, it needs to be addressed ASAP before any skin damage occurs, which can then result in permanent fur loss.
Also, the lack of appetite and skinniness is a concern. Dogs lose their appetite when something is wrong. Granted, there are finicky eaters out there, but most dogs love to eat and only get inappetance when something is truly wrong and they're not feeling well.
Toss the oatmeal shampoo - it's a total myth that oatmeal shampoo is good for the skin; it can actually make it worse.
Get something like this:
Amazon