Q.New holly bushes are losing leaves
I have planted 3 new holly bushes in a bed with another 8 or so old bushes. This is the second batch of 3 that I have planted because the first 3 lost their all of their leaves after about 3 months. This next batch has started to lose leaves as well. We are new to Venice FL where we are growing these. Is this an insect, animal or fungus that is removing the leaves? There is minor damage to the older plants but I have noticed some loss of leaves at the bottom of the plant.
In the attached picture, you can see that the leaves have just disappeared. In one picture you can see a couple of branches at the base of the plant. I just started using tri-mix on the plants in hopes of eliminating some of the creatures that are causing the damage.

Since your having issues with several plants, I would suggest a soil test to start out.
I soil test will help determine if you need to make some changes to improve your new plantings survival rate.
Your local County Extension Office can help with a soil test for just a few dollars.
This link will help you find your nearest office.
https://www.gardeningknowhow.com/extension-search/
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
In the mean time, pull back the mulch and check the soil conditions. Is the soil moist? You need soil to be well draining.
Also keep the mulch back at least 6 inches from the base of the plant.
You mention that these are new plantings.
With new plantings you need to keep the soil lightly moist. Never soggy.
After the first year you should water during dry spells.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/growing-holly-bushes.htm