How much water?

Since you are using airpots and add to that the fact that you aren't watering with much water and that's why your soil is drying out pretty quickly and you are watering every 2 days. You really should fully saturate the pot so all of the soil is moist. If you are worried about overwatering, don't worry that much about how much water you use. Overwatering happens when you water too frequently and keep the soil too wet. as long as the soil drys out a fair bit between waterings, fully saturating the pot won't cause overwatering. Does the plant get any more light other than the sunlight you are giving it outside? If not, you really should give it longer hours of light. Only 7.5 hours of light isn't a lot for cannabis. It really wants at least 16 hours when it is vegging. If you need any other advice feel free to dm me! Good luck!