The problem is not with electrolytes during a singe day's ride. It is rather a problem with dehydration as it results in a thickening of the blood and reduced circulation which resulted in the symptoms you experienced.
I go by the color of my urine to easily determine if my body needs more water. Studies have shown that the amount of water needed varies widely with individuals and so drinking X quarts of water a day provides no measurable benefit.
Electrolytes are important but you get enough with a good diet with green vegetables and fruits (bananas). Gatorade is heavily adultrated and whether in a plastic lined can or a plastic bottle it contains BPAs which are seriously detrimental to ones body. But Gatorade deserves an A+ for great marketing.