Hi ernie85017,

Yellowing of leaves or chlorosis can be caused by a number of things. Watering is always on the top of the list so in order to rule it out you'll want to start there. This time of year citrus need watered about once every two weeks as long as the water is soaking down deeply into the soil. The ideal depth is 3 feet, which creates a moisture zone that takes a while to dry out and enables you to water less often. It also encourages deep roots and the water carries salts down below the root zone. Salt accumulation can be lethal to plants.

The easiest way to water deeply is to create a 6 inch berm around the tree at the drip line. Some folks like to add a second berm about 12 inches away from the trunk to prevent water from reaching it. Filling the basin should provide adequate water for your citrus. Here's a link to the University of Arizona bulletins on citrus (including irrigation) http://cals.arizona.edu/maricopa/garden/pubs.htm#Citrus

Nitrogen and iron are necessary to produce nice green leaves but soils that are too moist can prevent absorption of these and other nutrients. That's why its important to let the soil dry out a bit in between waterings. We're talking wrung-out-sponge dry, not bone dry.

It's also a good idea to add a 3-4 inch layer of organic mulch or compost over the soil in the basin. This will slow evaporation, keep soils cool in summer, release nutrients as it decomposes and helps to lower the pH.

Lack of nitrogen usually causes yellowing of older leaves while lack of iron is seen in the new growth. To be beneficial to the plant, iron must be in an absorbable form. Ironite doesn't provide this but your chelated iron will.

Here's information on nutrient deficiencies in citrus. I hope it helps.

Here is a link that might be useful: Common citrus nutrient deficiencies and herbicide symptoms