Plants are probably running out of rootspace. That's why I suggested putting them into flower. Don't forget they'll at least double in size when you start to flower. That's probably why they're drinking the water up so fast.
Other factors like soil mix, humidity and temps, along with strain will determine how much they drink.
Feel the weight of the pot when dry, then water. When it gets to nearly the same dry weight again, it's time to water.
Judging by the size of them now I'd say you'll be busy with that watering can pretty soon
Good luck .. RBH