What sizes are you getting? If you are getting 4gig or more you might to test the performance running them without the 1333's (yeah, I know that does cause a warm and fuzzy feeling). If you have software do performance testing. With both in, and separately to see if you are getting what you want.
Guys need some help here
so far i have 2 x 4Gb Transcend 1333Mhz memory is it fine to add Team Xtreem 2133Mhz to them...
my mobo is the Gigabyte Z77-D3H