A week ago, my son (2.5 yrs old) started adding an “eh” sound at the end of words with an “o” sound near the end, such as no (becomes no-eh), more (becomes mo-eh), and go (becomes go-eh). In a similar way, car becomes caweh.

He could pronounce these words perfectly before -- the wrong pronunciation started suddenly a couple of days before we came out to California (where we'll be for a month, before returning to Ohio for another month).

Very odd. I'm treating it as a phase and hoping it'll go away.