Q.Meyer lemons black/dark covering on skin
Some of my Meyer lemons have a black/dark covering on the skin. Only the bottom half of the fruit. What could be my problem and solution? Tree is growing well. Fruit is firm, growing slowly, and some of the fruit is discolored. Is this a virus that can be cured? The color of the bad part is like charcoal. Solutions?
Sounds like a case of sooty mold.
You can treat with Neem Oil with good results.
Here are a few links.
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-meyer-lemons.htm