Yuzu leaves are yellowing from the top down, outdoors in summer and in greenhouse in winter, handwatered every other day, feed with citrus food monthly. Advice is appreciated, it's gotten much worse over the last couple days (was recently feed) and I am worried I will lose it.
the photos show classic signs of iron deficiency. If you have given them fertilizer that has iron chelate recently then the problem may be that the roots have become damaged due to over watering. Over watering can lead to fungal infection. Watering every other day sounds rather high unless it is in very hot dry conditions. Usually you want the soil to dry somewhat between waterings to help prevent fungal infection. Check the ingredients in your fertilizer. If it does not list iron (preferably iron chelate as otherwise you need to be careful about soil pH) then you may want to get a fertilizer with iron in it.
Sometimes citrus is not always the healthiest growing in containers (especially smaller containers). The difficulty is keeping the soil from completely drying out too much for too long, while at the same time making sure the soil is not overly soaked with water for too long, because that can begin to promote root rot and result in yellowing of the leaves like that. Care needs to be taken in choosing a proper soil, one that can retain moisture but still allows adequate drainage. I even covered the tops of the base of my containers with plastic wrap, to help slow down evaporation of moisture from the soil so it did not require being soaked with water so much. One more thing you might want to do is very closely examine the leaves to see if there are any tiny red mites. You might need someone else with good eyesight to do this since they are nearly microscopic. (If that turns out to be the case you will want to spray with a dilute solution of insecticidal soap, maybe even spinosad if you really want to be sure)
