Am I missing something ???

Sorry this is kind of long..

So i am a nanny for a beautiful 2year old girl

About a month ago I was questioned by CPS if I had ever noticed any signs of abuse on her such as bruises or anything un usual. I said no, because at that time I thought she was a normal little girl with her own personality. Well now that times past I’ve spent time with other children around her same age and I’ve noticed shes completely different. She’s quiet, she’s afraid to talk, afraid to ask for anything or say anything. She keeps to herself and it seems off. She’s taken a while to get used to me and my husband but now when she’s with us she’s happy and playful, but anytime she’s around her parents she’s just.. different. Recently I’ve been working on potty training with her and it seems to go well here but once she comes back from a weekend with her parents or even a few days she’s been just peeing herself completely. Not telling me that she has to go or anything, which is odd. Cps was called on her dad by his ex wife because of “abuse” on their two other children,

Could something be going on and I just didn’t see it? What do i do. I just want to keep her safe beyond everything else 🙁