Why is part of my foot discolored?

27 | F | 98 kg | 164 cm | Filipino | BC for PCOS

Hello, there's a bit of discoloration on my right foot that I'm quite curious about. It doesn't hurt when I walk on it or even when I press on it, but I just want to know if it's something I need a doctor to look at before it gets any worse. Right now it's brown, but sometimes it can be red.

https://imgur.com/7JxQHg6

If it matters, I have problems with my hips, knees, and feet. The first two are hyperextended (not diagnosed, they're just way too flexible) and I'm flat-footed. I don't remember when I first started noticing it, but it's been maybe a month or two? Coincidentally, I only started noticing it after I started exercising again, so maybe it has something to do with that, maybe. Not sure, I'd love some information.

Thank you!