Nice catch!
I would split them up into their own cages. That way you can keep track of who eats what, and make sure one doesn't eat the other one.
Here's what I keep my two in:
cages.jpg
The left is a 32oz plastic storage container from the dollar store.
In the wild I think Gonatista spend most, if not their entire life on the trunks of small vertical trees. Andrew and others have used this design and the mantids seem to like it. They spend most of their time on the log, and when startled they can run to the backside of the log as they would in the wild.
The "log cage" may be overkill, they may be fine without it, but it seems to work well.
For cages in general I found this post from bug trader really helpful
http://mantidforum.net/forums/index.php?showtopic=28467 I do the same thing for my smaller cages but add a few screened windows in the side and some furniture, and a foam plugged hole for "blow darting" flies in. Malakyoma has a great youtube video on building containers too.
The two I caught took a long time to settle down and eat, like at least a week. Watch their abdomens. When they are flat, they could eat something, when they are plump they may be full.
I've seen them eat small roaches, houseflys and blue bottle flies, but usually they eat when I’m not looking. I'll put a blue bottle fly in when I go to work and in the evening it's gone, and their abdomen is a little fatter. Usually they are on the log side away from me hiding.
Be sure to search this forum for "Gonatista", there are a lot of great posts from AndrewNisip about these.
And I see you have dirt in the bottom of the terrarium. While that's a beautiful terrarium, it makes it hard to see what they've eaten and makes it hard to clean the cage, in my opinion. You may want to go with just paper towels on the bottom and mist the cages a couple of times a day. Ventilation is important.
They all look nice and healthy. Enjoy!