Great job! It was DEFINTELY the wind!!
I think the key for those longer distances is having a solid nutrition plan(you do), learning to pace yourself and spin easy early (you do), and just plain getting used to spending HOURS on the bike! OY! You can do it. I have no doubt. I think it's prolly more mentally daunting than anything.
Again- FABULOUS JOB! Don't forget to get back on that bike and spin super easy to help those legs recover. Also- one other thing I do after a long effort is find a way to ice down my legs. Right now it's to jump in my 55 degree pool. But if I go to a race I make sure my hubby has bags of ice on hand at the finish line. I really feel it in poor recovery if I don't ice after a race or long ride/run. I think that is key for us long distance gals.