Sometimes the snakes don't have a good enough grip on their prey to coil after. I've noticed this with my girl, especially when she was in shed. I personally don't feed her in her tank, I take her out, and even though some say it can stress out the snake, my girl has always had a great feeding response! I can hear she strike the moment I place the top of the separate box. There was one or two times when I could hear her thump against the side of the box, then 30 seconds later, I can her grab and coil the rat. I personally wouldn't be worried about the strike and miss. Next time just drop the prey item in. Don't dangle it or anything, and if she misses, don't re-pick it up, just give her time, and keep a eye out to make sure the prey doesn't harm your snake (I just recently ran into that problem). I wouldn't be worried about your tank being to crowded. I feed my girl in a box that is just the right size. This is just my own two cents being thrown out there. By no means am I an expert. I only own one ball python and I've had her for 3 months. This is just my own advice based on my own experience and from reading other's post's that where given for advice.