I have a 5 year old house. Our Guest room never gets warm, the office (bedroom) is only slightly better and the Master is just about 10 degrees cooler than the living room, the master has 2 vents. I noticed that there hardly any air coming of any of our vents when the fan is running. I can hear the fan running and the house stays warm except for the bed rooms. I've found if I leave the doors open they are more evenly warm but if the doors are closed they are cooler I would think the opposite would be true, as it is in my parent house. Any suggestions on where to start?

Check for a dirty air filter.

Your system might need to have the ducts balanced to allow proper air distribution. I would call a HVAC company and have that done. They have air flow meters that make the job easier. It could also be a problem with your duct work and they can tell you what the problems are when there looking at the system.

Since we cannot see your duct work and take readings here it has to be done ON Site.