A three gallon pot will hold b/t 1/2 and 1 gallon of water depending on how dry it is. I used coco last grow, and I was surprised at how much water would go in before running off, and how heavy the pot was when watered. Even with soil, you should try for a bit of runoff when you water.
DLI is a way to measure the amount of light your plants are getting. DLI chart and thread This post talks about it but it’s long. The main gist is the chart, and that you can get an app for your phone (i-phone or android) that allows you to measure light. It’s called Photone. I have the free version, and the sunlight setting was found to be the most accurate for indoor growers.
I was accidentally hammering my clones which I was holding in a small tent and one of them got weird top leaves. The tall one is getting more intense light to the top than the smaller one, so she may be getting too much.
And of course, it may be hot up there.