The teeth on the front are meant to be used for harder bites but not for long chewing sessions.
I grew weird massester muscles after I started chewing with premolars and front teeth pretty hard for months:
Before
After
As you can see, even after I lost some fat, my bottom massesters are now smaller and the muscles in the middle area are larger...
I will only chew with back teeth now.
Do you know a way to undo this? I am scared about that even if I only use my back teeth the muscles on the middle grow larges, because I can't really isolate them.
It seems like weight loss (maybe de-bloating, less water rentention, etc.) and you being too being overly-particular to your masseters. They look fine to me, imo, I don't think what you experienced it enough to come to a general consensus that anterior dentition is worse than using the molars. Also the incisors are used for incising and the molars for mastication so it make sense to chew on the molars.