Certified GKH Gardening Expert
It may be lacking nutrients. I would fertilize it, as they are heavy feeders, especially when fruiting. Here is more information: https://www.gardeningknowhow.com/edible/fruits/citrus/fertilizing-citrus-trees-best-practices-for-citrus-fertilizing.htm
In addition, you may want to conduct a soil test to see what specifically may be missing. You could also add some phosphorus (like bone meal) to the soil to help promote blooming and fruiting.