2020 Rav4 Tail lights scaling like crocodile

Help what the heck is this. First I thought I had a smashed tail light. I was loading somethings in my trunk and saw on both sides the same kind of interior marks. They appear to be within the plastic housing. Micro cracks inside. Perhaps from heat I have no idea. I welcome your input. I am the only owner. No accidents. 7,600 miles ODO 2020XLE. I park in uncovered parking, temperature is average 90 degrees with 70 percent humidity and it pours every 3 days or so.