Water Leak Question

[wengerda]

Here in the Northern Virginia area had 3 days of non stop rain. That is good fro the grass. when I checked my camper on the third day I found maybe two small drips of water in the rear side window. The drip was so small that the drip did not drip into the carpet. It came from the bottom portion of the window and drip probably 4 inches. I know that on the outside of the window is caulk really good. By the way the drip was dark like 'rust' color? where I should check. Water leaks are not good but at least is a small leak, but I want to stop it now.
Any suggestions.