Baby Jackson’s and fruit fly difficulties!

Here’s The hardest thing I have come across keeping fruit flies in the enclosure! I put a small piece of fruit in there but they keep on getting out and this raises a big concern because the babies need a supply of food at all times. I’ve heard of bean beetles being good feeders. Just really frustrated and not only that my female that just gave birth 3 days ago is acting restless even at night no lights on the enclosure probably going to have more very soon and that is a good possibility. I have dubia roach colony and there quit a few baby roaches but I have never used them for new borns. If anybody out has some pointers it would be greatly appreciated!