There was no reason to throw away the lettuce and there would be no reason to throw out the peppers. Those may be Aphids but it is difficult to tell from the picture. Do they fly when disturbed? if so they may be White Fly rather than Aphids.

A simple method of insect control is a sharp water spray that knocks the wee buggers off the plants. The buggers may return or the next generation may appear. Just keep up with the sharp spray of water.

Diatomaceous Earth would not be a good control for either Aphids or White Fly. Insecticidal Soap is.

kimmq is kimmsr

They are aphids. All you need do is miss squishing/spraying one and the population regenerates.

Whiteflies don't sit on top of leaves.

About 2 weeks ago I had the same problem with my tomato plants. I filled a spray bottle with about 3 drops of non bacterial dish soap, a teaspoon and a half of neem oil and water. 2 spray applications and the bugs are gone! It's been 2 weeks and the plants are back flowering and creating new fruit!