Help, why did my pictures get rejected?

Hey,

I am uploading for the first time and got my photos send back with the feedback "quality issues".

I made sure, that the size of pixels and MB is alright. I also read a little bit about grain and contrast being a common reason for refusal, but I couldnt see that problem wih my pictures.

I have attached 2 examples below.

Maybe someone can tell me how I can improve the pictures?

Thank you !