Thanks for the response!
Unfortunately it is probably too late to take another logic course, since I've already graduated and I'm applying this cycle. One of my professors said to mention it if I have something to say to explain to the admissions committee. Since I really don't have a good excuse (I suspect "it was the pandemic" will seem pretty pathetic, while the more honest "I just didn't care about formal logic back then" would only make the situation worse), I'll probably take your advice and not mention it.
SXS0P8HDYL got a reaction from Jim VK in Got a C+ in Intro to Symbolic Logic: am I doomed? (And should I mention it in my personal statement if not?)