Gardenia 'August Beauty' Problems

I have a gardenia that will not thrive. I have a number of the G. jasminoides veitchii that do well, even the G.j. radicans is healthy...but I cannot seem to make the 'August Beauty' happy no matter what I do.
Soon after purchasing and repotting the leaves began to turn white and drop off. Now a whole side is dead and the other side does not look well.
In the photo you can see the veitchii on the left, next to the ailing 'August Beauty' on the right. Both plants were purchased at the same time.
My area has a lot of fungal issues; black spot, shot-hole, verticillium, etc. My Japanese maples, years old, started slowly dying back as well.
Is this likely disease and is there any hope for it?