Hello, those do not appear to be the typical areas where mange likes to infect. It does look more so like the areas where you can find fleas and flea allergy dermatitis. However, the only way to look for mange is by obtaining a skin sample and looking at it under a microscope and sometimes, even if that test is negative, Charlie may actually still have mange.
I would ensure that Charlie is having adequate monthly flea control and see if this helps any. If he continues to have these spots, then the next step is to have him tested for other parasites such as mites.