Start off the 4th day, here in Agra with an early morning tour of the Taj Mahal, as it gets rather crowded during the rush hours. Moreover, the beauty of the Taj, captured under the morning sun is better than any other sight you will see.
For the rest of the day, 2 more attractions are scheduled for you, the Red Fort, and Itimad-Ud- Daulah. The rest of the day is open to you, to spend and enjoy as you please.