The air returns you have in those 2 bedrooms *may not* be designed to pull air. Sometimes builders put in jumper returns. These essentially are pressure breakers, when the room fills with air when the system is on / doors are closed the excess air leaves room via the jump duct return.

The main filtered return that draws air is in a hall way and the jumper duct termination vent is typically placed somewhere near the filtered return.

Two rooms having weak air flow could be due to a number of issues. It could be due to design of the duct system (long runs) / refrigerant issues (low on freon causes the indoor coil to freeze) when that happens air flow will be hindered.

If your system is older low air flow can be caused by failing blower motor that doesn't fully ramp to proper speed. (Just because the motor spins doesn't mean it's working properly -- I changed one of these just a few weeks ago -- while this situation is rare, it does happen.)

It's hotter than a fire cracker. The more heat the easier it is to discover the flaws with an air conditioning system. If you're running the AC system in record breaking temps -- the system is operating in conditions that it wasn't designed for.

It's been in the triple digits 101-102 with index / feel like temps in the 110 to 113 range where I live in Katy, Texas. What are your conditions like? (this will impact poor designs in a myriad number of ways)

For these reasons & probably others -- it's in your best interest to search for a licensed AC contractor in your area and have your AC system inspected by a pro. ( Enthusiasts / home builders for mild climates may chime in with other ideas / just because you read it on the internet doesn't make it true.)

I service the Katy, Texas area.

Hi, E,

Your home's HVAC system should be designed to produce comfortable conditions in each room of your home. That requires designing duct work to both supply the required flows of conditioned air to, and return it from each room. Each bedroom should have a return per best practice. You indicated both inadequate supply and return air flows in two bedrooms. That's most likely an air balancing issue. Getting proper air flow--particularly to rooms farthest away from the air handler-- will often require balancing of air flows. If your duct system is equipped with balancing dampers, you can adjust them to direct less air to some rooms and more to others. You'll find them at branch connections to your main trunk line. Here's a link to a video which provides a clear explanation:

https://www.youtube.com/watch?v=8dJbLTEXyfg