Hard/blur shade lines around newly added faces Im very much a beginner so the things ive tried are:

Pushing individual vertices deeper into the head this resulted in a decrease but not a fix:

Ive tried to use &quot;Smooth Vertices&quot; but this didnt help.
Reapplied subvision modifier but outcome didnt change.

Has anyone had this before and knows how to solve it or why this happens?
Added a picture of my mesh without subdiv modif visible in viewport.
Instead of creating new vertexes and then using the fill hotkey F, I was able to resolve this by extruding 2 new edges and merging vertexes with existing ones. Then extrude 2 more edges and merge all vertexes and in this way I created 4 new faces that dont have any issues. Still dont know what caused it but this worked to solve it atleast.