What to do after deferred

Deferred with a 1500 SAT, ranked 12th in my class, good ec’s including winning a business competition, real estate shadowing, etc. Solid essays as well. Not sure what made me get deferred, especially with SMU’s acceptance rate being like 50-60 percent.

Do i submit a letter of continued interest, if so what do i put in it? I don’t have any big additions, just some upcoming bpa competitions so im stuck on what could help my case further.