No. If the krill is large and the lion is small, make sure you break the spike off the head of the shrimp first. Normally they do best on live foods such as mollies and guppies. If he is getting stabbed inside his mouth or stung by something and getting a sore, it could affect his jaw snap but, without trying a living guppy to trigger is strike, he may just not be able to eat sometimes because it just doesn't move right for him. Shaking sounds like he is trying to shed something thats floating around in the water and getting stuck on his head or eyes. Do you have any tube anemones of similar in there?