Two gallons of water does not seem like much for all 5 pots. The runoff may be from watering to quick before it has a chance to soak. You are doing it slowly, but if it's dry below it could take a bit for it to soak up.
Do the pots feel light all the time, like a day after they are watered?
Do the pots feel light all the time, like a day after they are watered?