Why is my puppy loosing hair?

My 14 weeks old puppy is loosing her hair around her face and forehead area.  At first, I wasn't worried about it but now it seems to have gotten worst in a week.  I searched the web looking for answer and they said it could be cause by many things such as:  stress, flea medication, diet, or the worst some kind of disease or it could be some kind of flea infestation allergy.  So it could be any of those and what do most recommend?  Take the puppy to a vet.   and I don't have money for a vet visit.  So I'm going to try to change her diet and carefully monitor her outside scavenging activity.  So if any of you might know why my Pitbull puppy is loosing her hair or fur please reply to this blog.  Much Thanks

 

Puppy Hair Lost