Sometime ago I've read bl novel that description for Tyrant Pampering Wife Diary made me remember of it. There was this (second?) prince that was poisoned and it caused rage fits or something like that. He was also slowly dying because of it. I think uke helped heal him. I tried searching for it, but I can't find it. Maybe someone has some idea? Please?
Tyrant Pampering Wife Diary is a completely translated work. Hope it’s what your looking for. https://www.novelupdates.com/series/tyrant-pampering-wife-diary/