I would say, if you had 4 powerbar gels you probably weren't suffering from a lack of sodium or potassium. If I recall correctly, these are the primary supplements in endurolytes, no?

If that's the case, you might just have needed more calories. I find that I get cramping when I am not consuming enough calories...

Living in FL, I'm surprised you had big troubles...other than its JANUARY and still hot and humid!!! UGH. Anyway, I've found that Hammer's Endurolytes are the BEST electrolyte replacement. In the summer here, I use at least 3 per hour, and sometimes more. I like the powder form because I can mix it into my SE in the bottle and not worry about popping pills. You need to use trial and error to figure out how much water and salt you lose during training, and how much to replace. Too much however can cause a sour stomach I've found. Good luck out there!

E-Load is a sports drink designed for high heat/humidity conditions. That may be worth a try in hot and humid conditions.

The trick is to balance hydration, electrolytes, and calories. Too much of the latter two and you'll get sloshy and gastric trouble. Too much of the former and you'll bonk or cramp. I ran a similar hot/humid half-IM last July and got whacked with leg cramps. A competitor gave me what he called a Lava Salt tablet. With that and two Gatorade cups every mile, I was able to just barely stay ahead of the cramps. I think my problem came from not topping up enough with gels and supplemental salt at the end of the bike (in part because I was worried about getting a sloshy gut). Live and learn.