Plant collapse

The leaves on this plant called Strobilanthes atropurpurea suddenly started turning black and now the whole plant has collapsed.
Can anyone suggest some reason for this and any advice on what I should do with it ... it has one new branch with unaffected leaves but I'm afraid this will also go the same way.
I can't find any information on line

 

Hello Michael, I had a look on the French sites and can't find any reference to known problems. It sounds and looks like a sudden fungal attack. On the bright side, it's considered almost impossible to do unsuccessful cuttings, so I'd do some quick from the remaining stem!

 

Agree it does look like some fungal problem, though could it also be a severe case of red spider mite as well ?

 

Thanks for replies and advice @JWK @noisette47 @ricky101
It could be a fungal attack (can't see evidence of red spider mite) so I've cut all the dead stems off and noticed some new growth coming from below compost level. I may treat it with a fungicide and hope for good results.
I don't think it can be vine weevil because the leaves all turned black and crisp whereas with vine weevil I think they would have wilted.
I may tip it out of the pot later on when I get a chance to have a look at the roots, maybe there's another problem there.