VFXCode:
I suspect that it's the MOSFETs not having enough time to turn off? Shouldn't MOSFETs turn on-off times be at 100s of nanoseconds?
MOSFETs have internal capacitance, some more than others, see your datasheet.
OTOH I'd suspect all those capacitors in your circuit before the MOSFETs. What exactly are they for? It looks to me like they might be keeping the LEDs lit up for a short time after your MOSFET switches off.