what could cause this?

Hi
I’m getting lines drawn on my mesh that i didn’t draw. On the pic i just drew a patch at the chest and these lines were drawn as well?How can i avoid this happening and why is it happening?this is a smart uv unwrap.

I tried all the other auto unwraps and they have the same issue with this model

even happening to a lesser degree on a makehuman model. If i’m painting a hand a small artifact might appear on the cheek etc? how do u prevent this?