Note the small, dark splotches near the heads of the torch in the middle of the first photo. The torch on the left is thriving, so the torch on the right has either been damaged or nipped at.
Second photo is a strange worm or snail attached to the sick torch.
Can you post a pic with white lights on? Red is kinda hard to see. I get that it helps spot thingamajiggies that come out in the dark, but at least a pic with flash would be super helpful!