I have several pots of swedish ivy and one had been looking pretty "yellow". I didnt think it was gonna make it. So I wouldnt have to see it die I put it in my green house
and only checked on it occassionally. (I really hate to see them die) Low and behold the plant started to look better and better. Now it's joined the garden once again and has been looking well since then. Im not sure if the humidity or my ignoring it that helped it but it could be something you might want to try. If you dont have a green house
just get a large enough plastic (I sometimes use the bags comforters come in) and keep it in a make shift green house
for a while. Good luck!