| My feeling is a fungus too. Sorry - no help here only sympathy... I also have hoyas (4 - not rope), which have the exact same problem - for at least 12 months now. As you say, they still flower really well and frequently, but the leaves look pretty terrible - its mainly with older yellowing leaves, but still get it on newer green leaves. Mine live outside - 2 get morning sun, 2 get arvo sun. They are watered regularly which they tolerate well (its always dry here), fertilizing, pest management (aphids), or new soil has no beneficial effect. Hopefully someone has an answer for us! I'll be devastated if I eventually lose them after so long... | 
