I use ProMix as well... and I never water until there's runoff! I've got a couple of ladies in 3-gallon fabric pots who are now almost 5 weeks old and I'm giving them 1/2 gallon at a time... if there is any runoff, I wait for a half hour or so to see if the pot/soil soaks it back up - if not, then I pour off the excess in the saucer and I'm done.
At the stage you're at, I would be watering perhaps a quart of water in ever-widening circles around each plant... I do this because I don't know what the roots are doing, where they're going and I want to make sure they're all getting something to drink (I also add microbes to strengthen the rootball and ensure they are able to take in any nutes they need - i.e., prevent lockout). In about a week or two, you can start soaking the whole pot. As always, wait until they're bone dry and the pot is super light before giving them another dose of water/feed!
Good luck - they look great! 😊