@captainjamestkirk46 - I would say right now that you’re NOT in trouble. Colleges pay attention to FINAL grades, not quarter grades. So, even if you don’t pull up any of these C’s during this quarter, if you did better in previous quarters (or expect to do better in the last one), then you shouldn’t be in trouble at all.
If, however, you do finish the year with C’s in three classes (which seems unlikely based on what you’ve said), there IS a chance that your Purdue acceptance will be rescinded, but it’s more likely that you’d just get a warning letter instead.
If your grades continue to slide, you should take measures to get back on track. Speak to your teachers about suggestions on how to improve, attend extra-help sessions if offered, engage a tutor (peer or paid), use Internet resources to help you understand the material, etc. Not only will these tactics help you to raise your grades again, but also if you keep a record of what you’ve done to stay afloat, you can submit this to Purdue if there is talk of a rescinded acceptance. College folks are much more sympathetic to students who struggle in tough classes but continue to try than they are to slackers whose grades go down due to lack of effort. So just make sure you document your effort.