What size tub? Maybe consider moving to a 15qt for a little while until he starts eating better. Also make sure he has at least one hide.

It sounds to me like he is hungry, but maybe too insecure to actually eat what he has killed. Next time you feed (one week) leave the lights off and put the rodent in with the snake and leave it there til morning. If it isn't eaten overnight then throw it out. Obviously if you are doing live you should monitor the feeding. If he doesn't kill it within 10-15 minutes then remove it and try again next week.