Yellow leaves with green veins
A yellow-and-green pattern has several possible explanations.

What to look for
Compare new and older leaves and check recent watering, roots and growing conditions. A nutrient uptake problem is one possibility, but yellow tissue and green veins alone do not identify which nutrient is missing.
What to do
Start with drainage, root health and appropriate light. Avoid adding concentrated fertilizer or iron without evidence. If the pattern continues, a local extension service can help assess the plant and growing medium.