Iphone muffled sound?

Whenever i plug in my earbuds my iPhone 8's sound is muffled. I've tried cleaning inside and tried new earbuds but nothing is working. Any suggestions before i take it in to get it looked at?

My iPhone cases always turn to a dark color?

My last case was a beige color and after months of use, it was a dark purple. I recently got a white case but that is now a dark pinkish color except for the part around the camera. I haven't been able to find anything about this. Does anyone know why this is happening and how i can possibly revert the colors?

How long would damage be noticeable to iPhone from water?

I usually listen to music when doing chores around the house, so I put my phone in my waistband and listen with earbuds. Not to be gross, but on days that are hot my phone will sometimes get sweat on it and I usually just wipe it off, but it probably gets a thin-ish layer of sweat on it frequently and it stays on frequently. Today I had to clean things outside and my shirt got damp, not drenched or dripping water, but it's still a little moist thirty-forty minutes later. I still had my phone on and probably for 30 minutes after I initially got water on me. My phone is an iPhone 8 and it has no visible signs of being damaged. It feels dry (currently) on the outside, but it has a case on. Could water have gotten into the microphone or speaker at the bottom? Has fire ever been a hazard when phones get wet?