You check string height by putting a capo on the first fret. Fret the 12th fret with your finger. Around the 7th fret, you should be able to just
slide 2 business cards under the strings. That is the right height. You might want to check your intonation also.
If you changed from a heavy set of strings to a lighter set, this can also cause buzz if the truss rod is not re adjusted. Did you get your guitar set up?