You can over-fertilize.
The only problem I have seen when over-fertilizing is that some varieties with a particular leaf-emergence style grow so fast that the leaves get tangled inside one another and don't emerge properly. Others show no issues that I have noticed, at concentrations/amounts that cause the leaf tangling on some varieties.
You are probably overdoing at about 1# of 15-15-15 on a mat/clump per 10-14 days.
There is not much point in fertilizing when bananas are dormant (nights below 55F or so).