If he is 3.5 years old and those are his baby teeth, then they are probably ready to fall out and grow adult teeth. The first set in the middle will fall out at 2.5 years, the second set(the ones you highlighted) will fall out around 3.5 years, and the next set out at 4.5 years, this goes for the top and bottom teeth. So if they look like the gums are raw and maybe brusing a little bit and the teeth look dead, I would say they are gettin ready to fall out.
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"