You could very well be right however, it is surprising how much electrolytes we lose trough sweating/exertion. That and the fact that drinking water by itself will leach out those precious minerals. Combine that with the relatively high amount of water you drink in order to replace what you lose working outside in the heat tells me it is a distinct possibility. Still, admittedly, doing a diagnosis by comment replying is not a exact science to say the least. Best of luck, and health, to you.