We have just upgraded our HVAC system in our 100-year old house in GA. After a few months of running this new system which has three zones, we feel that the house stays very humid and we see mold on our registers and on the carpet around the registers. What gives? The system is adequate (we can drop the temperature quickly if we want to) and we didn't have this problem before. They have changed the size of the return air ducts (I thihnk it is a little smaller now). Could this have caused the issue? By the way, the house is in no way air-tight.

Thanks for any advise,