Failing gooseberry bushes

My 5/6 yr old gooseberry bushes used to be extremely productive. About three years ago the sawfly started and at first did not affect the crop. Last year I got no fruit and every leaf was decimated, so i kind of feel the plants had no benefit from the lovely but late summer we had last year.

This year I set the hens in amongst the patch in the hope they would eat the sawfly larvae. I see no sign of caterpillar damage yet, but the bushes have flowered and it seems the flowers have not set fruit. (or at least very little)  Lots of the flowers just fell off.  The leaves have gone darkened around the edges as well.

 We have bees and plenty of pollenators. The is no issues with the blackcurrants or redcurrants setting fruit.

Anyone any ideas?

Thanks BQ I'll search for the other thread.