blackcurrant problems

HI

Blackcurrant bushes are 5 years old and up to now have been really productive. This year was great.  Now they look like this and it doesn't look right.  Any ideas?

I don't know whether to chop them right back - but there's buds all over them so I'm reluctant to do that. 

Ah, thank you. I've had a google and that looks likely.