We can't tell you as we aren't psychic. All we have to go on is whatever you tell us and any of a number of things (or combination of things) could cause a score drop. 7 points really isn't worth fretting over IMO.
What changed on your report? Is there nothing in the Credit Report Activity section?
JasonB wrote:I'm 21 now and I just opened my account the middle of last month.
A credit account? An account on this site? A CK account? The former could certainly cause a score drop due to a drop in AAoA and a hard pull.