@ rpdladhrwl - My guess is that your acceptance won’t be rescinded. But you should be proactive and contact UIUC now and try to explain your downturn. If you struggled with illness or added responsibilities at work or at home, be sure to say so. You can also mention that the accounting course was outside of your major, but don’t make it seem as if you didn’t care about it because you didn’t find it important. Instead, however, you can say that it was unfamiliar material that was difficult for you.
When students appear to care about poor grades, admission officials are more likely to give them a break than if it seems that they don’t care.
Good luck!