2.5 tons is right in the edge of being able to handle 1400 sq ft. Where do you live? It is two story or one? I think your AC might just not be about to keep up. Nothing wrong with it.
Growing up in the southeast, every AC unit is too small.
Something to consider would be a portable/window unit to compensate in high traffic areas/bedroom. Used to use that to cool a room and let the rest of the house run a bit hotter instead of fighting the outdoor heat.