How will 1 C+ 1st quarter as a Senior taking 6 AP classes in a 7 class course load affect me?

Due to a lack of sleep, near constant quizzes and tests, the our school being behind schedule, I bombed one of my AP Econ test and did not have much point recovery options. I ended up with a C+ 1st quarter. Otherwise, my grades are As and Bs.

My first quarter grades were included in the transcripts that were sent to my regular decision applications. Assuming my SATs are good and my extracurricular are okayish, how bad does this look?

I’m doing better 2nd quarter and will likely raise my grades in that class to a B or higher by the mid year report.
Is trying to go for an Econ/math major out of the question? Should I just apply undecided? Is it bad for me to put undecided but put econ and math in my essays as academic interests? For highly selective colleges I mean.

I am a Korean American male. No math ECs.

Colleges: Ivies to NYUish, like highly selective 6% to 30% ish.

SAT: 800 CR 720 M 690 W, 760 SAT MATH 2, 710 World History

Extracurriculars: (9-10) Chess Club, Japan Club,Marching Band (11-12) Coauthoring a book (examines the Korean Wave, the increase in the popularity of South Korean culture, with several other students), Taekwondo, National Honor Society
Volunteering/Work Experience Midnight Run (distribution of food, water, and basic toiletries to the homeless of NYC) (9-10), about 21 hours; Summer Internship at Delegate David Bulova’s campaign (July to August 2015), about 8-10 hours; School Band Fundraiser Raffle (10), 6 hours

Honors and Awards: National Merit Scholarship Semifinalist , AP Scholar, National Honor Society Inductee

One C+ won’t destroy you, just bring it up for the semester grade. As far as I am aware, most colleges only view semester grades to begin with. I don’t know what you define as elite but I got into UChicago with a C+ in AP Physics first semester, though I had a good excuse and I am Hispanic so… Who knows?