The evaporator might be freezing up, which could be due to low refrigerant or possibly a buildup of dirt and debris. Both can affect airflow and cooling performance, so it might need a recharge or a good cleaning to get it back to normal
That's brutal! 33k miles is way too soon for that kind of wear. Definitely sounds like the previous owner dropped the ball. Sucks you had to drop that much for something that should've been avoidable