It's possible that it's become too cold overnight. Although you're a little further south than me, I've had a temp of 4°c overnight a couple of times this last week, which really is too chilly for chillis! Also, they don't like to have 'wet feet' overnight, so it's best to water in the morning if possible. Finally, if they get too hot & dry, red spider mite move in - they're really difficult to spot to begin with, but a bad infestation will leave very fine webs over the plant. The symptoms of spider mite are a gradual yellowing of the leaves to begin with, then the plant starts looking really sickly. To prevent them, keep the atmosphere humid, to get rid of them, you can get biological control (ie., predator insects).
I'd advise nipping off any dodgy looking leaves to prevent botrytis (grey mould) taking hold, keep them damp & warm (but not soaked & cold, or dry & hot....!) and maybe spray the remaining foliage with some sea-weed solution.
__________________
Sarah
“Tell me one last thing,” said Harry. “Is this real? Or has this been happening inside my head?”
“Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real?” | 
21-06-2008, 05:59 PM
Chilli plant help needed! 
They are in the polytunnel on our plot along with peppers and tomatoes which all look fine. I can't see any evidence of aphids although I have used the soapy water spray a few times.
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