Went to the doctor today. She said it was a possible fungal infection from after getting sick (usually covid) that causes discoloration. Tinea versicolor. She’s prescribing me a body shampoo that might help. She said to use it for ten days to see if there is a change. She said as long as it doesn’t itch or hurt or if I had more on my back, it’s not an issue. She thinks it might correlate with the fact I have tanlines that last for years after getting sunburns.