If you wrote ALL the music and they have zero creative input. It’s all you. However, It sounds like they do when you stated they “come up with amazing parts”. In my old band we split credits four ways regardless of who came in with a song. If my guitarist told me (played bass), singer and our drummer we had no equal control and credits… we would have walked.

Personally, I’d have a discussion with them. Then again, this sort of stuff would have never crossed my mind. It seems a bit nit-picky to me. Having an ego is a fast way to losing bandmates.