Worried about skin darkening and prediabetes.

Hello everyone! About a year ago my A1C had risen from 5.4-5.6. I freaked out and cleaned up the way I ate. I’ve always been an avid gym goer but I guess I could’ve eaten healthier at times. I was also getting super poor sleep. I avoid sugar, high glycemic carbs etc. I drink a lot of Coke Zero and Celsius but nothing with sugar. Nervous about acanthosis. But can’t tell if the elbow stuff is from planks from my hot yoga class or if it looks like it. Same with pits and back of neck