You can get them to come out in the morning also... but mine never stayed out all day.
Basically, you can coax them out to eat by squirting a small food like cyclopeez in it's direction, and feed in the AM and they will eventually stay out longer and longer. Bad side to this, is the food you use to coax them out doesn't usually get eaten... so it adds nutrients. I did this a few times but ended up just giving up and enjoying it at night lol.
The good thing about your colony is that it is still small, so it should be relatively easy to spot feed each head without wasting too much once they are out. I would only feed a small amount, maybe one or two pieces at a time.
You can kind of see how yours acts... like I said mine was only happy with daily feedings... others only feed two to three times a week. If it closes up for more than a day or two you may need to coax it back out before you can get it to eat again which can be really frustrating.
Once you find a routine that keeps them happy they do fairly well.