My Hoya plant moved with me to this address ten years ago, although it is much older than that. It has always been happy in my conservatory, having had over 100 blooms, both times this summer. It is now about twelve feet high and has a spread of about ten feet. Just lately a lot of its leaves have very suddenly turned yellow, mostly they are at the base of the plant although there are a few more dotted throughout the plant. I have never fed it - just gave it rainwater, but now I think it desperately needs some first aid of some sort. Please help.
Red
