I think it looks bad regardless of your major/background. When you are coming into a postbac with a lowish GPA, you need to get mostly As and basically hit it out of the park. If you are a non-science person, you have even more to prove in terms of demonstrating your ability to succeed in the sciences.
To the OP: one C in the sciences is not fatal. But it doesn't help your cause. Do what you can to get mostly A's in the rest. If you find you need to slow the pace of the program or cut back on ECs, work, etc. to get A's from here on out, by all means do so. Good luck.