possible pepper problem

The mature leaves of my peppers are turning mottled and curling at the edges. Some are developing brown patches and others are turning upside down. Can anyone tell me what is the problem? They are just beginning to flower.

 I was wondering whether to start feeding them despite the fact that they have not set fruit yet. Is it something missing in their diet or are they just unhappy about the weather. They are in a raised bed underneath  PVC.

Cheers MumofS Have done. Sunshine has come out as well