Looks like mold or fungus, but hard to tell just from the picture. You're in MA, I don't know what kind of snowfall you had this year, weather, moisture, etc.
Your grass looks more like a clumping type, so I'm assuming it's mostly PRG/TTTF which won't spread. My hunch is it's likely a northern mix. I know quite a few members have issues with perennial rye and winter kill.
In just the bad areas I would probably lightly loosen the soil and seed either perennial rye or tall fescue, knowing that it may die in the heat of the summer or have weed issues and focus on preventing this in future seasons.
Ideally you would have a high percentage to KBG that you could push to spread and fill the areas.