Dermichlor spray. Apply twice daily on affected areas. Keep the puppy clean and dry. Do deworming sincerely.

Very common in puppies , upper spray recommend can work , if not affective try coconut oil mixed with turmeric , if still continues consult vet then probably allergy if wheat or grains containing gluten

Friday also suffered this type of rash, his skin was sensitive to the floor cleaner Lyzol, we switched over to a pet friendly brand, which did the trick, plus do not allow Shiro to sleep or lie down on dampy surface