Peppers

These are/were growing beautifully.  They are orange ones, in the conservatory.  They are infested with whitefly, although could be green or blackfly, I dunno.  Tried bug spray, didn't totally work, tried washing up liquid.  After washing up liquid the leaves started turning yellow/black dying, do you think I made the mixture too strong (I did make it very strong), or is it the fly attack.  They got really sticky, but don't know if that was the bug spray which smells like WD40.  This is the second mishap I 've had with these peppers, I tried moving them and broke off two branches lost 9 peppers.

Ta