The home is 5 years old and both sides of the garage door have cracking outlining the header. I’m looking for some input. Thanks in advance.
How much does the header bear on its supports?
Looks like a normal settlement/shrinkage crack to me.
What in the heck is plastered all over the interior walls of the garage?
And to me.
Must be the paint!! 
Marcel
**Paints : Architectural : Interior Paints : **
Cover Quick Latex Flat (034) A production flat latex paint designed for drywall and plaster. A high hiding wall paint which can be used for new construction, apartment repainting or general maintenance painting.
Product Color Quart 1
Gallon 5
Gallon034171 White
034144 Largo White
http://www.mabpaints.com/images/Globals/msds.gif http://www.mabpaints.com/images/Globals/techdata.gif
Is it a skim coat that may be cracking?
Looks llke common cracks to me.