My pepper plants have yellowing on the lower leaves that started small about a week ago and is spreading upward through the plant. Zone 7, in a raised bed, transplanted in May, and they've been carrying a heavy load of fruit for the last month — probably 15–20 peppers across four plants right now. I'm watering every other day, deeper waterings not shallow ones. No spots on the leaves that I can see, just an even yellow fading to the veins. Soil drains fine, not sitting in water. What am I looking at?

Pepper plants heavy with fruit, with some lower leaves showing yellowing
Attached photo · Photo: Anna Evans / Unsplash