HEALTH UPDATE:
Two other mysteries solved...
1. CURVED LEGS
I've had larger nymphs come out of a molt with curved legs. I finally got to witness this happening. A large female molted a few inches from the front glass - the only surface not (yet) coated with something gripable.
When she was stabilizing herself, I watched as she tried over and over to brace herself with the foot, unable to grip anything. She did it so many times, that she re-shaped her leg in a curve, and flattened out the hooks on her tips.
After about an hour, that leg was worthless. So, when it came time to flip and inflate her wings, since it was one of her front legs, she couldn't get the angle right, and the wings were perfectly straight, but wouldn't close completely. Wish I'd have gotten pictures.
He overall look was not DIS-similar to the female pictured above. She is more lethargic than her sisters in the same circumstances, and I'm doubtful of her survival chances.
I will probably/possibly add a thin "ribs" to the glass (similar to your rear window defrosters).
2. MESSY WINDOWS
A long time ago, I posted that the back wall behind my screen enclosures looked like a Jackson Pollack painting - all splatters of something or other. I thought it might be blood and guts that squirted out when my Idolos & Gongy's bit into a fly. But I finally got to see what it really was - first hand.
I had never noticed before that my mantids didn't JUST have solid waste. But I watched an L4ish mantis shoot out a small jet of liquid from his hind quarters. It looked like a cat spraying a bush with urine. Where it hit the glass matched the spray on the wall. Somehow, I had never seen that happen before.