If you look at page 49 of the installation insructions I linked to there is a troubleshooting form that will gather the information to answer many of the questions Ladia refered to. It would be good to have this information anyway for future reference in case the geo contractor decides to retire and the system needs service by someone else.
I would give the contractor an opportunity to step through this. There are several possible reasons the system is not performing to expectations. THey are all objective.
The geo system may have a problem or not be setup properly. The form I refered to will direct them to that.
The air side of the system may have a problem. Checking the static pressure and the fan speed settings will detect a too restrictive system. Further checks of static pressure and temps can dectect leaking returns or supplies.
The pond loop may have a problem. Ladia covered alot there.
The system may not be sized properly. You said they did a load calc. You can compare.
The building envelope may not be performing per the load calc. This gets a little subjective because they have to do a best guess baring a full energy audit, but were their assumptions reasonable.
