Need to see the problem really, any chance of a photograph?

Hi, welcome to GoY, as Bamboo says we really need to see a photograph before any advice can be given.
Hoya really need to be grown in a mixture of equal parts, John Innes number 2, leaf mould, sharp sand,pulverized bark, and charcoal, not just peat, { poor old pete, lol}, it could be this that's causing the problem, Derek.

Gosh Derek that's a complex mixture - I have two cuttings ready for potting on - isn't ordinary potting compost with John Innes adequate?

Hi Sue, well you can use ordinary j i, but that is the usual recommended mix, they're a bit picky, lol, Derek.

OK thanks. though epiphyllums and christmas cacti are epiphytes that are happy in ordinary potting compost. But the hoya perhaps deserves some special treatment, its certainly a beauty so perhaps they have a right to be picky!!

Hi Sue, it's because they need really good drainage, but with good aeriation as well, plus they need a very moist atmosphere, that's where the charcoal comes in, your right they have every right to be picky, lol, Derek.

I guess I could just add some perlite then, and use a fine water spray if the atmosphere gets dry. Or stand them on a dish of damp grip like cyclamen.