Bad Bell Pepper problem

Best guess would be red spider mite, they are tine and very difficult to see. Someone will be along to either confirm or make other suggestions.

Have you sprayed them with water? The brown marks could possibly be scorch. I've had pepper leaves turn themselves upside down before without apparently coming to any harm.

looks to me like the leaves have been watered

I had some tiny White aphid living in the new growth of a few of my pepper plants this year,I've never seen them before,I noticed it because the new growth was coming out twisted looking. Some older leaves do naturally twist around,but this was different. I squirted them with a bit of hand soap & water,it was a delicate operation,the bugs were in new leaves that were 3mm small or smaller,I left the plants outside in the open & the problem seems to have gone.
Was the sun out when you sprayed with insecticide & did the brown spots appear after using it? I watered with plant feed once when the sun was out,i had brown sunburn spots like that the next day. The holes in the leaves are probably from slugs,I had the same on some of my plants when they were in the blow-away grow tent,I've planted them out now,some are undercover. Slugs have left them alone now & are more interested in the french marigolds I've planted everywhere. It's good to have a few sacrificial plants to lure the slugs away. I have about 50 marigolds sowed from seed into plastic cups,just to keep the slugs happy (whitefly also don't like to nest near the roots of marigolds) they're a great companian plant.