Bigger tires add rotational mass. More weight, more terrain, steeper descents. Your stock brake pads were not spec'd for any of that. Brake fade is the kind of problem that sneaks up on you and then hits hard. Swapping to pads with better heat tolerance is one of the cheaper upgrades on this list and one of the more important ones.
Sixity carries powersports brake pads for pretty much every ATV, UTV, and motorcycle brand worth naming. Good resource if you are maintaining more than one machine at a time.
Most newer riders typically start with the flashy stuff. Wheels, a leveling kit, maybe some lights. That is fine, but the builds that hold up on the trail are the ones where the fundamentals got sorted first. Here are seven upgrades worth doing, and the order actually matters.