Red in the face

[suitable4frank]

When feeding my littlest lotl worms he sometimes goes really quite red in the face as well as his gills fluffing up lots and you can see his little veins.
It's usually when he's got half of the worm still hanging out of his mouth. As soon as he's got it all in and eaten, he'll go back to normal.
He's about 4 inches long now and I always make sure to give him worms no bigger than an inch which have come fresh from my garden (no harmful things in them).
I've not ever had this problem with my bigger ones.
Any idea what's wrong?

 

[Bette]

I notice this with my white axies too. All worms seem to secrete a yucky substance when the axolotls chomp them (red wigglers are the yuckiest apparently). So this seems to be a reaction to the taste and perhaps has something to do with the excitement of fighting with the worm.

 

[Hoagii]

My 3" leucistic gets very flushed at feeding time. Her gills get red and sometimes her face even looks a bit flushed. I figure it's probably just because they go from their usually loafing about to striking and manipulating worms, they get a bit of a work out. You figure it's got to make their little hearts beat faster.