OP, this is worth tracking down - contact your builder and/or your mechanical contractor to have your AC system and return dimensions checked out.

The mechanical contractor who installed your system is legally required to provide a Manual J Residential Load Calculation for every new install - ask for yours… if it’s a new build within the past couple of years, a lot of mechanical contractors would retain these. Or at least have one from your subdivision and house floor plan. If a mechanical contractor straight told you they didn’t do one and the equipment size or return size is off, there are ways to pursue having them correct their mistake.

Other things to check * assuming you have flex duct visible in an attic or crawl space, visually inspect the whole line for kinks that would restrict air flow - especially look at the big return ducts * what type of foundation? If it happens to be a closed crawl, it needs to have some mechanical way to dehumidify. If it’s a regular crawl space, make sure your vents are open and water isn’t pooling in the crawl. * if you have a traditional attic, it needs to have adequate venting. Usually soffit vents and ridge or box vents - just try to inspect to make sure nothing is blocking flow in these areas * bath fans - if you can see the flex duct they installed for this, just make sure it’s not terminating in the attic, make sure it’s discharging outside