I'm a rising junior in a top30 US university. Last semester I got a C(2.0) in undergrad Partial Differential Equations and a B in Complex Variables (this course is a undergrad course but the prof taught it by the curriculum of a grad complex analysis). My expected graduating GPA now (after the C) is about 3.7. How will this harm my MFE application? Will taking a grad PDE and Complex Analysis course (and getting As in them) help? What about taking Duffy's Differenial Equations courses? (Also I got COVID during last semester, and I believe my memory and energy was really harmed by it, can I use this as a reason in the additional application essay?) Thank you all.