My citrus trees eat whatever I give them, and they love it. At least two hands full of pelletized cow dung a season and two to three applications of micronutrients. We have been getting fruits for the past 3 years, outdoors in northern Europe. They are wintered indoors though.
Lemons and limes get everything a lot quicker than other citrus, here yellow leaves mean greening, but I doubt that would be the issue in Idaho, so probably a deficiency. If you have scale look for ants too, they go hand in hand or mandible in mandible or whatever they have. I've found that treating for the ants helps a lot.I had a scale problem on a lemon that was really hard to find and destroy.
Yeller leaves might mean pests.
Sorce
ants