Would you recommend retaking classes during undergrad when applying for grad school?

I'm currently a senior, my GPA is currently 80% (3.45/4.3) in CS. My undergrad is only 3 years and during my second year i got a 3.1/4.3 due to some personal stuff and me focusing on research. I got a C in an important subject and a B- in an optional class and mostly B+/A-. Should i retake my C and B- classes by delaying my graduation till the summer ? I feel like i can get a 0.15-0.3 GPA increase if i retake them