Ok, can you show us the back of the bottle, please Keith? Need to see what's in it besides the N - P - K. How much did they use and how often?
Any idea about how much water they're giving the plant, too? When the weather cools, you need to water less, but if then you still fertilize the same amount, the fertilizer is not diluted by water so much, so instead of getting less fertilizer for cooler weather, the plant gets more.
So . . if the plant gets a dose say, once a week through the summer? Then you'd give it the same amount but maybe only every second week, or half strength once a week would also work. Taper off through the fall, until half strength once a month in winter would probably be enough - again depending on where it's growing in the winter.
