Sick lemon tree
Lemon tree not making lemons, leaves are green trimmed in yellow.
Certified GKH Gardening Expert
Yellow leaves are normally either a lack of water or a lack of nutrients. It could also have too much nitrogen. Make sure you are watering correctly and give the tree some slow release fertilizer. Additional phosphorus can hellp with fruiting. These articles will help with fertilizing your tree: https://www.gardeningknowhow.com/edible/fruits/lemons/learn-about-fertilizer-for-a-lemon-tree.htm