I already assigned two recommenders, and they both submitted their recommendation letters. However, both of them are in the same area (math & biology), and my french teacher wrote me a great letter that focuses on different aspects other than the two letters. Would it be wise to add the french teacher’s recommendation in the common app now, as to add more depth to my app?
(I did not submit any additional recommendations)
Other than saying you have a great facility for foreign language, I cannot imagine what a FL would say that your Math and Bio teacher did not. Do you plan on majoring in a foreign language at college? If not, I don’t think you should submit it, as it would be a 3rd letter from a teacher. Additional letters are helpful if they come from adults who have a different perspective on an applicant, such as a research mentor or an employer. However, a third teacher recommendation might water down what your other teachers have already said. Remember, “Less is sometimes more!”
FWIW: If you haven’t submitted your application yet, the other option might be to add the FL teacher to your Common Application and delete either the Math or Bio teacher from your list of recommenders. That way, just your two strongest recommendations will be sent.
I already submitted my application as I am applying early action. However, what’s so important about the french’s letter is that it gives more insight to my personality rather than my academic and social skills, which I believe is important to colleges like Harvard. It mostly talks about how I contributed to my school as a person rather than as a student. So, what do you think?
Your feedback is very appreciated 
As you already submitted your application, my recommendation would be to let it go. However, if you feel that your essays, other teacher recommendations and interview report will not convey your “personality” then go ahead and sent it.
Well, I think I would let go, as both math & bio recommendations are excellent.
Thank you so much.