You could re-arrange some of the live rock a little to confuse the two other tangs. Also, keep the lights out for the night until tomorrow to keep the stress level of the naso down.
What size is the naso? Unless you have a small one, he should't be picked on at all. Especially in a 150. How big is the yellow? Which tang was the first in the tank? The thing about the yellow being in their first is that he is pretty territorial. The naso should be pretty docile...just my experience and .02 worth.