Drivers vents (Dash & Floor Vents) Blow cold

I have a 2002 Buick Park Avenue. Most vents blow warm
air when the heat is turned on. BUT, the drivers vents in the
dash and the floor vents blow cold air while all other vents
blow warm air. Also, when I turn on the windshield defrost
setting, the drivers side of the windshield defrosts so
much slower than the passengers side. What can I do to
fix it?

Note: I have recently been to a mechanic for an oil change
and to have transmission fluid changed. I had him check
my cabin filter and other air filters, all filters have been
replaced and are brand new. The old cabin filter wasnt
super dirty either.