There are several possible reasons. The usual ones relate to a frozen evaporator coil, dirty filter, dirty condenser coils, a leak somewhere in the refrigeration system or possibly in the ductwork system. It could also be that your unit is older and simply not able to keep up with the extra heavy cooling demands with our weather changes these days. ProSolutions Inc. can check this for you, identify the issue, and advise you on the best actions to take.