I have my VFT inside where it can't catch bugs on it's own so I feed it live bugs from time to time. Some of the 'Mouths' look very healthy, they are a nice green with a little red in the back, but when I put a bug in I make shure that they trigger the little hairs but it still woun't close on the bug. When I move it to another 'Mouth' it well eat it without hesitation. Sometimes I have to try 2 or 3 different leafes before it well take it, what would cause this with healthy leafes?