Prefabs with parts overlap

I have a prefab consisting of a few different parts. Currently I intstantiate them inside a container.

When I have Instantiated a few of them all of the parts that are the same are on the same sorting layer so they overlap, this is something I don't want.

I've tried to change the sorting layer for each part and in Game mode I see it works but they still overlap. What am I doing wrong or how can I fix this?

//This looks like its working as intended but my prefabs still overlap.

 GraffitiLetters[i].GetComponent<Letter>().GetComponent<SpriteRenderer>().sortingOrder += 100;