Yellowing Leaves On Meyer Lemon

Question

This tree is about 5 years old and lives in a 14″ pot filled with cactus soil. It generally does not get overwatered. The Persian lime next to it is doing fine. The leaves on the lemon are yellowing and dropping fast.

• 
• 

Answer 1

There are a few possibilities listed in these articles:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-leaves-turn-yellow.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-leaf-drop.htm