Outer labia darkening?

Not sure if it’s due to POF/HRT or not, but I’ve had POF for about a decade at this point, and about 5 years in or so, started noticing my outer labia becoming darker in color overall with some slight darker splotchiness here and there (possible melasma?). It’s the only area on the body where I’ve experienced any skin color changes. Has anyone here experienced anything similar?

I do wonder if it’s possibly just due to age. I’m close to 38.