Does your fan make them parts of the leafs tickle each other and cause a abrasion? Almost look like there could be rub in a few of those spots but honestly throwing a dart with an observation on a couple pics. Or maybe u just damaged the leafs in those spots pulling back your covers?..?
I honestly wouldn’t worry tho since they low bc it is kinda dense under there. If the rust spots start popping up more places then I’d start to chase my tail.
Idk if it’s ever as simple as just need more P bc it’s not in my brain