Don't mention fruit SG. I once had a plum tree outside one place I used to live at. God knows what variety it was, but from the effects the fruit had on me, I imagine they must have been the main ingredient of Ex Lax.
Obviously I didn't suspect this at the time, eating 3 or 4 pounds each day for a week before getting the message.
SG, I imagine that it being only your second race, and at 11 miles also, the problem was caused less by overhydration but more through a combination of heat, lack of appropriate fitness and massive effort.
I'll admit though that I went through a phase of gut problems which may or may not have been connected to hydration.
Understandably one becomes a bit more cautious after a few rounds of that.