What have you fed it.?

Why have you allowed Bermuda grass to grow underneath a newly planted tree?

When / how often have you irrigated?

Where are you located?

For starters, it's not a good thing to plant a citrus or any fruit tree in the lawn. It will get to much water. It is normal for a young tree to drop a lot of it's fruit due to its own immaturity. Fruit will typically drop in June because that's just part of it's natural cycle. Citrus drop whatever they cannot handle during this time. I am going through the same thing myself and am very disappointed. Growth beneath the graft should be removed. Anything above the graft can be kept if you wish. You didn't mention application of fertilizer. Have you ever fertilized the tree? If so, what did you use?

Your tree is hungry and thirsty. Citrus roots are poor competitors for food and the grass will uptake any nutrients you place on the surface before your lime tree has a chance to absorb them. You need to clear a ring of grass around the trunk in a 4’ diameter to start. Every year you will have to expand the cleared ring as the canopy of your tree grows. You also need to add a separate irrigation drip line or bubbler to water your tree deeply, not daily for a few minutes as you would water your lawn. If you don’t have another drip system you can run a line from then you can use a garden hose and water with it a couple times per week. Once you clear the grass and start watering properly you should see your tree start to improve, that’s when you should feed it with a granular citrus fertilizer 3-4 times per year starting in the spring. Follow these steps and your tree should do fine with time.

Evan

Thanks everyone for the feedback! The nursery where this tree came from believes it's an overwatering issue, but I do think the grass growing under the canopy has caused a lot of issues, When planted initially (May 2018 ) with organic 6-4-6 fertilizer and mulch it had a healthy looking amount of leaves and no grass growing under it. It gets hot in Los Angeles where I am so was watering every couple of days. Attaching 2 images of what it looked like in June 2018. You can see the brown spots in some of the leaves were happening within a month. I will definitely try creating a ring and watering less/and or trying a drip line, but just making sure no one sees this as a diseased tree that should be removed.

Yeah, got a little worried since I wasn't sure if it was related to some kind of fungus or bacteria.I started pulling the leaves off that had those brown spots, but then no new growth started happening except on the outer fringes of the branches. Wondering if I should prune off the bare branches to stimulate new growth, or if that would shock the tree?

I am going to have to respectfully disagree with the assessments above. The symptoms of overwatering and underwatering are virtually the same. Once you clear the area as I suggested and water deeply to reach the roots below the grasses roots your tree will begin to leaf out and improve. When your tree gets water right now it is most likely a shallow fast watering that will only keep your grass hydrated. This is what my lime trees look like.