Gabrielle,
I have sandy soil also.
When you have sandy soil, you know the problem is making sure that our trees and shrubs and plants are watered enough, the soil doesn't hold moisture very well.
Adding compost really helps with holding water, but what I have found is not to plant the tea olive or any shrub high, above the soil level.
Plant it at least to the soil level, (the rootball) or even better, plant it a little under on purpose.
When you water, the water will puddle a little if the shrub is planted a little bit lower, and the plant can get more water down at the rootball.
You stated you mulched, it needs alot of mulch all around the rootball also, but not at the stem.
It is suffering from lack of water. That is why the elaves are turning brown and dropping off.
Go out and very carefully dig it up and dig the hole deeper and replant it a little lower this time.
Try 1 inch lower than the soil level.
Before you put the mulch back on, leave the hose on it, and make sure it is placed right at the rootball.
The water should flow down to the rootball and start to create a small puddle and then slowly flow down to the roots. (in other words make sure the water is going down the rootball.)
Really soak it.
Then after you soak it real good, then reapply at least 2 inches of mulch all around the plant.(not to stem).
Don't put a trench around it, you want to water it every day for a week and when you place the hose on it, you want to see the water run down to the stem of the shrub.
After about a week, if it doesn't rain, then water 3 times a week if it doesn't rain.
Taper off on the watering per your temperature outside.
It needs extra watering right now because it is dying from lack of water.
Eventually, when you see a big improvement, and the daytime temps cool off a bit, gradually water it a little less frequently.
Don't forget to water it in the winter if it doesn't rain for 10 days in a row. It still needs water, and it is young.
Remember, sandy soil is great for tea olives, but extra watering and composting every year along with good mulching is crucial in order to grow anything in it.
Good luck to you, and I hope your little shrub is OK.
They are my favorites!

Thank you so much for such a comprehensive reply! I will immediately do everything you suggested and hopefully it will rebound. Again, I really appreciate the time you took to give so much information!

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