Weak airflow on opposite side of the house.

All - We bought our house about a year ago and it has a ~12 year old Goodman PCKJ036-1 package unit for downstairs heating and cooling. Total distance from the unit to our master bedroom and bath is about 50 feet and the downstairs living area is approximately 1800 square feet. We live in the southeast portion of South Carolina.



The rooms closest to the unit are the most cooled and heated and the master bedroom (farthest point) is the least cooled and heated. The unit does not seem to struggle to heat or cool the first floor, but the farthest rooms are roughly 10 degrees off of the rest of the house.



So far I have done the following. The filter is clean and replaced, I inspected ducts in the crawl and all were attached with no kinks/leaks. I opened the unit and confirmed the fan speed is set to high and the blower fan spins freely and is clear of obstructions.



I am looking for options and/or opinions here to make the master suite more comfortable. Is an inline blower fan a bad idea? Should I install baffles in the rooms closest to the unit to force more air farther down the line? Is my unit undersized and I am SOL? Should I attempt to find a higher speed blower motor? Thanks for the input!

Weak airflow on opposite side of the house.