One of the most common problems that the home gardener have with there pepper plants is the yellowing of there leaves. This can be caused by a few different reasons. The first is the lack of nitrogen and magnesium, another reason is chlorinated water, soil splash on the lower leaves from watering and a fungal problem.
The first reason, the yellowing of leaves is most of the times caused by a lack of nitrogen and magnesium in the gardens soil. This can be simply a result of the nutrients being leeched from the soil due to excess water. Pepper plants only need 1" of water per week. Another reason is the plants may need an application of fertilizer that is high in nitrogen to get past this problem.
Normally you wouldn't want to give pepper or tomatoes a high dose of nitrogen, it will usually result in lush foliage and not a strong harvest. You need to get the plants healthy again, so if they need a dose of nitrogen do it sparingly.
Another thing that works for me is to apply an epsom salt spray to my pepper plants. Epsom salt will supply magnesium and calcium that can be absorbed by the leaves for a quick recovery. You may want to try this foliar spray. I mix 3 tablespoons of epsom salt to one gallon of water and spray the foliage.Then I apply a slow release organic fertilizer that is high in nitrogen to the soil around the plant. At this time I remove any flower buds so the plants can solely concentrate their energy on there foliage. There is still plenty of time for a productive harvest.
If chlorine is the problem, you can simply rid the water of chlorine by just running the water into a bucket and letting the bucket stand for a few hours to allow the chlorine to evaporate.
Lower leaves that turn yellow on your pepper plants can be simply caused from soil splash when watering. They will yellow and wilt. Remove these yellow leaves and your plants should do just fine.