Found In a car engine .. rescued and now in need of a home

Pending euthanasia

Ok so I recently (1 month ago) adopted a one year old chihuahua female. I was super scared to adopted a dog since my childhood dog traumatized me. He was prone to a lot of illnesses and had seizures, so when he passed I was scared to adopt another dog. Well 2 years go by and I adopted this dog. They told me she was only 1 year old but I suspect she’s younger? Her teeth are super white and she loves chewing on her toys so I feel like she might be a few months old. Well the problem is when I adopted her she was way more “cleaner”, idk if that’s the way to put it but let me explain. The first thing I noticed about her when I first adopted her was her really white b**hole. I noticed this right away because my previous dog had the darkest hole ever. In addition, when I first got her, her girl part was also really pale and now it looks really brown and stained. Also she tears a lot and when I first got her, she would never tear. Another things are her paws, she is brown in color, but has like white paws, like little socks, and when I first got her, her white paws were super white. Now they are dirty looking and the dirt doesn’t take off even though I scrub them after every walk. All to say, I feel like I’m making my adopted baby worse? She looked better when I rescued her. What am I doing wrong as her owner? I don’t mind her looking this way if it’s normal but I feel like I might be doing something wrong? If anyone knows what it could be, could u please enlighten me.