In somewhat of a dilemma...

I would just be honest with both of them. Tell them that you asked both to write recommendations because the deadline was coming up quickly and you wanted to be sure to have at least one available to write you a great recommendation for your five schools. Tell the one that responded first that since you've also received a response from the other professor, you have asked the second professor to write letters for two of your schools, so he only has to focus on the remaining three. Then tell the second professor the same thing.

The key with this approach is that each professor should write at least one letter for your top choice school. That is, don't give your two safeties to one professor and the other your top three. Give one your dream school and your safety, and give the other the other three.

As long as you are diplomatic and honest about the situation, frankly, I think both professors will appreciate having to only submit a letter to two or three schools instead of five. You could also frame it as being thoughtful about their time- five recommendation letters are a lot for one person to write in time for November deadlines.