How do I fix these faces? Weird shapes I'm having a problem with the faces in the corners of this pillow where they keep reverting back to a weird jagged shape that's very noticeable at certain angles.







I tried adding an edge in the middle which worked but then I have triangles which I would rather avoid. I also tried dissolving the edges but the faces did not keep that shape and just went back to how they were. I also tried removing the faces and manually filling them again which worked but only once like here:



I'm not really sure what else to try, any ideas? :(
Thanks
Click the faces which have that problem and subdivide those.
Or

Use a subdivision surface modifier(would increase the poly count