I've been feeding mine a steady diet of earwigs, and sometimes spiders. They have caught a few flies on their own, but I try to keep all, but 1 or 2 traps fed in order to keep them growing optimally. My traps have gone from looking dormant, to starting to finally make longer traps with the 400 watt metal halide, only 1-2ft away, and bigger traps.
Here's my DCXLs, All but 1 of mine from before ended up dying because someone watered them with tap water, but now they have been sent from my parent's house to my place, and that solo survivor, looks like it is doing well here. It went from 4 traps, to working on getting up 7 now in 12 days. I ended up purchasing a new DCXL because I wanted to fill out my pot quicker. All these pictures were taken July 4th, and July 16th respectively showing the increase in number of traps and trap size.
Before: This was my original DXCL
After: This is looking much more healthy now, progressively making bigger and bigger traps each time.
I just purchased this one a couple of weeks ago. This DXCL looks quite a bit different than my original in that it was lighter, and had an overall different shape, but it's traps are pretty big, and progressively getting bigger.
After: They look darker too, now that they are exposed to strong light.
Here's the G16 which doesn't look quite as impressive, but it should come along after the initial shock. I have split it apart from the parts which appeared to be wilting away to hopefully see if the old stuff recovers, and the new stuff keeps growing uninterrupted.