My pepper plants are starting to get yellow around their leaves. Are they getting sick and what can I do?

I have grown peppers for years and never had this problem. They are in pots, receive enough water and also fertilization. The ones that became yellow do not have any buds for flowering as of yet. What can I do to help?

My pepper plants are starting to get yellow around their leaves. Are they getting sick and what can I do?
Are the pots big enough? Enough sun? the right kind of fertilizer? Going yellow sometimes means low nitrogen in the soil. Good luck.