Answer: That is puzzling!
Since all of your other plants seem to be growing just fine, I suspect the problem is with either that particular patch of soil in the garden, or with those particular pepper plants. For instance, occasionally something gets accidentally spilled in the garden that will affect the soil, such as excess fertilizer or lime or gasoline. More often, though, the plants themselves are to blame. If they were severely rootbound before planting, or were somehow severely stressed, they may fail to thrive. One other possibility is that they have simply failed to root into the surrounding soil. If you don't mind experimenting, dig one up and see if that is the case. If so, you might try unravelling some of the roots and replanting the plant, then treat it with TLC just like a new transplant.
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