Planemaker, you don't say what food or gel you may also have consumed on the 50 mile ride. When I do a two hr or less ride I only take two bottles of water if it is cool, if hot I put Gatorade and possibly electrolyte capsules in the bottles. For hard rides longer than two hrs I will take a bottle of Gatorade per hr of riding. I also eat Hammer Gel or Cliff Shots at @ 300 calories per hr beginning from the get-go on long rides. I understand that the body can supply two hrs of stored energy @
300-350 calories per hr from stored fuel in the blood, muscles and guts and supply 250-350 calories per hr from fat and process up to 300 calories per hr from calories you eat and drink. By eating right away I dont deplete the stored energy in the first two hrs. So in a nut shell I have about 700 calories per hour of fuel in my body for two hrs work, unless supplementing, and once I use them up I begin bonking unless I slow down and use fewer calories or supplement them via eating. Specific training plans can increase the body's ability to process stored energy that would enable better performance.
I have bonked a few times due to ignorance, poor planning or change of routes. Bonks can beat you down for a week or longer and they are something I avoid by proper planning.
Hope you recover quickly.