Rust on Fushias

I have rust coloured dust on the underneath of the leaves. I have smoked them in the greenhouse, but its still on them. The leaves die and drop off although they are still growing and flowering. Any suggustions welcome.

 

it is what you say rust buy a fungicide spray
1.take off all infected leaves if all are infected take off worse
2.clear any old leaves on ground as spores lay dormant and can overwinter on ground to spread elsewhere
3.lighten up on watering
4.spray all over top and underside of leaves
then repeat in 14 days it should be fine

 

Thanks brazil I will give it a go.