First, the coolest temp you should try to attain is a setpoint of about 69 in residential. There are some folks who want it cooler than that, and some equipment can indeed get you there, but 54 would be bordering on refrigeration.
Second, ask yourself, when did you perceive this change? The beginning of the season? On hot days only? After you heard a noise form the system?
My point is that if the parameters are in place, and there was no work performed, then a supply temp like 46 should be cooling your house.
It may be time to get another opinion, since we generally can't rely on readings that we haven't taken ourselves.
My gut is telling me there is more to the story. Not that you are deceptive, mind you, but that there may be other pieces to this puzzle.