Random mild bruising on my face?

Just a week ago, I noticed a small dark bruise under my chin. I'm almost certain I didn't bump into anything and I'm definitely not an easy bruiser. Never have been. Anyways, that bruise disappeared within a week. Now I just noticed a second bruise on the left side of my lower cheek. Definitely didn't bump into anything and it looks the same as the first one. Just small, round, and dark. Does anyone have any clue why this would be occurring and especially on my face??? The only thing I could think of is possibly my Epiduo gel I put on nightly. It's for acne that my dermatologist gave me, but I've been using it for a year now and never had anything like bruising occur. Any ideas. Please and thank you!!!