Gate drive pins for the mosfets are usually the far left pin, if you look at the side of the mosfet with the part number on it. It appears that R32, R34, R36, R38 are gate resistors. I can't tell whether the color code is Red,Black,Red (i.e., 2000Ω) or Brown,Black, Brown (100Ω). Both are possible, but 100Ω is more likely. Please confirm the colors.
If you trace the gate circuit back, you should find what is driving it. A typical circuit might consist of PWM generator --> gate driver --> gate resistors --> gates. Sometimes the PWM generator and gate drive are integrated into a single chip. A gate drive is needed to generate the current needed to turn on the paralleled mosfets quickly.
If I were to change the drive for a unit, I would attack it at the PWM generator. The chip labeled TC4011BP is a quad NAND gate. It may or may not be involved in the gate drive. Anyway, if you can locate and identify the PWM generator/gate drive chips, there may be a way to change a resistor to change the duty cycle.
For example, the TPIC2101 and LM3524 are older PWM generator chips. The SG3525 is another common generator chip. Their cycle can be controlled with resistors and or capacitors. If you can locate the chips doing the same function on your board, then you might be able to reverse engineer at least the PWM generation part of the design and change its duty cycle.
Failing that, I would strongly recommend against trying to design a standalone drive for the mosfets, disconnecting the current gate drive resistors and inserting the new drive and appropriate resistors. The most likely outcome from doing that would be to destroy the device. There is almost certainly some sort of feedback from the mosfets to their controller.
John