I just got a Fender Squire Fat Strat for Christmas. Been playing for 15 years, and it's not a bad guitar for

the price, $300. My question is, the stock strings on it were ok, no string/fret buzzing, however, I changed the strings a few days ago, and put on Ernie Ball Super Slinky 9's, and I am getting some slight buzzing on the A string when I fret on like the 5th-9th frets. what's up with this? Should I bring the guitar back to the store I bought it from so they can take a look at it?