Unity Terrain - Grass Visual Artifact

Hello Dev'ers,
I seem to have this issue with this black/green line under my grass

My initial thought was that the photoshop file had excess pixels filled in under the sprite, so i went and erased anything underneath, trimmed the edges & selected the sprite and moved it to a new photoshop file.

Still none of those resolved the issue.

I tried importing an asset from the asset store to see if the same issue came up, something similar but different was this..


Was wondering if anyone has come across this, or knows a fix, is this a visual glitch in unity? or the assets themselves