Two plants, even two plants of the same genetics, even two plants in the same size pot and with the same media, even two plants that are clones of the same mother, can take differing amounts of water for various reasons. Damage to your root system from previous over/underwatering can leave a plant with less developed roots and make it unable to handle the same amount of water as its fellow.
Considering the size of your plants, it is possible you have been chronically overwatering since you transplanted into those pots. I would really, really try to let it dry out next time, and then water again. With your plants going strong 1 gallon of water for 5 gallon pots isn't excessive, I use 1 gallon of water for 3 gallon pots in flower, but those are established plants that have been in their pots for a few weeks to a month. It could be excessive, however, if your plants' roots haven't grown to fill out your pots.