If deficiency symptoms appear on old leaves, the problem could be from lack of nitrogen, phosphorus, potassium, or magnesium.
NITROGEN (N) deficiency causes rapid yellowing of lower leaves
progressing up the plant. Includes Pale plants, reddening stems, a dull or dingy leaf appearance, retarded-smaller growth. Usually the deficiency will be noticeable on the lower part of the plant, on the older leaves. then, as it progresses it will move upwards towards the newer growth. Unlike a magnesium deficiency, nitrogen def will start from the tips and work its way back to the leaf node.
Most of all it will stunt growth severely!
Pale plants, red stems, smaller growth. Rapid yellowing of lower leaves
progressing up the plant. Add any chemical fertilizer containing N.
Treated plants recover in about a week.