Hi, 

We would recommend that you do not apply anymore pesticides until you know what the problem could be. 

Fungicide is rarely warranted nor is it curative. If needed fungicide needs to be applied before the symptoms occur and then on regular intervals per the label directions. Even then if environmental or weather conditions are appropriate fungicide may not be helpful. Over use of fungicide can be harmful to bees and can alter the soil biome by affecting the microbes. 

You can look at the branches that are dying and see if there is any damage on them. Otherwise prune them out and feel free to take a photo of the branch and send that to us and we can see if there is anything noticeable that is causing the die back. You can also examine the interior of the tree and see if you notice any scale along the leaves, branches or bark. 

The at the base of the trunk, where it connects to the soil, can you see the root flare where it extends out into the soil? It should look like the stem of a wine glass. 

To our knowledge there isn't a specific disease or fungal issue that occurs with hollies, it could be physical damage from a squirrel or other wildlife. 

Emily