As I recall that toilet MaP tested at around 350 grams per flush it is not rated on the current report except as being WaterSense certified which means a minimum threshold of 350 has been reached.
Not the best toilet but it certainly should flush okay.
I'd look at all the usual suspect areas for not flushing good...
Something lodged in the trapway
Low water level in the tank
Blocked ports under the rim or, siphon jet
Blue goop bowl cleaner in the tank....