Bench press is a pushing motion whaich while done for chest, is greatly influenced by the triceps. So when you press, you are working triceps (pushing motion). If you are going for size and are lifting very heavy poundages, I would hazard a guesss and say that you are probably overworking your triceps if you do them on Wednesdays. Bicep work on Wednesday is OK though. Remember to get growth, in addition to proper nutrition, your muscles need adequate rest.