Riiiight. Here's some peppernoob thinking/assumptions out loud, courtesy of me Thought it would be simpler to post here than your "leaf problem" thread.
It sounds/looks like they're in a fairly soilless mix (cactus mix = peat, compost, sand, perlite/verm?) and that you have only fed them once? The leaf problem seems to be concentrated in plants you have topped?
As mentioned in the other thread, getting a handle on watering is numero uno before trying to diagnose. I learned with coco and it has been an uphill battle with peat so far