I have a three month old (cream colored) french bulldog puppy. Hes growing like a weed and very healthy except he does have a upper resp infection and on antibiotics for this. However I noticed within the past week where his tummy and skin is/was pink is starting to turn dark like around his ears, under his butt, his hind legs, and looks like splotchy dirt on his tummy where I assume is going to turn dark too? I know their skin can turn dark but he is a light cream color and didn't think with him being so light he would turn like this. He seems to be the darkest under his butt so far. He has no itching, no bumps, very smooth skin and doesn't bother him at all just me as a worried mom. French bulldogs are rare around here I live in a rural area that the vets look at me weird every time I come in because I'm so worried over my dog. Please help ease my mind or tell me what to do. Thanks!

It's nothing to worry about.