Iron deficiency in plants typically appears on the youngest leaves first, which is why I asked which leaves the problem starts on. Where the symptoms start helps narrow down the nutrient involved, if it is a nutrient issue, because some nutrients can be moved around to where the plants need them and others can't. Symptoms on the youngest leaves first suggest a nutrient that can't be moved around, symptoms on the oldest leaves first indicates a mobile nutrient so the plant takes it from the older leaves to give to the younger growing ones. This article has some pictures of nutrient issues in citrus that may help:
https://edis.ifas.ufl.edu/ch14...
Do you have any idea what your soil pH is? That can also help narrow things down.
