if you are drinking too much water that will cause an electrolyte imbalance.
i'm a big fan of drinking a lot of water yes, but there is such thing as drinking TOO MUCH. i've always found it silly how guys who weight train in an A/C gym seem to think they should be gulping gallons of water. you don't need all that water. go run in 90 degree heat and 90% humidity like i do and then come back and tell me who needs water and who doesn't.