I noticed my snow pea plants turning yellow/white in the lower half but they are green in the upper half and producing pea at the top. I guess they are dying?
It is normal for some of the lower leaves to turn brown and die as the plant progresses because the lower leaves have done their job and they are then finished. Their job was to get the plant to producing adulthood, that done, they then can die. When the plant is ready to give it up, then the whole plant’s leaves will beginning to turn light brown all at once. At least this scenario is the way it goes here. But what gets my attention are the dark brown/ black spots on the leaves brown and green. Perhaps you should investigate that.