I don't mean to be a wanker but I'm good at appearing so and I'm going to tell you like it is...
You have stacked the deck against yourself by:
1. purchasing an import true redtail with who really knows what background
2. putting that boa in a 55 gallon aquarium (this is really hurting your chances of success)
3. offering food on consecutive days (getting feeding wrong with a true redtail can kill it)
You can't correct number one so lets move on to fixing what you can. If you want to increase your chances of success this is what you should do:
That boa has probably (and hopefully) lived its entire short life in an opaque shoe box sized tub...and you should put it back in one. Go to the store and buy a food grade Tupperware type thing that is about the size of a shoe box or a little smaller. Poke some holes in it and put some aspen bedding in the tub with a small water dish. If you are heating that fish tank with undercage heat place about half of the new Tupperware over the in floor heat. Leave the boa alone for a week...don't even look at it. After a week place a fresh killed mouse of the appropriate size in the tub and walk away. Check on it a couple of hours later, if it ate, close the lid and change the water the next day and leave it alone for another week. After it eliminates that meal, repeat and leave it alone with only cleanings/water changes for at least 3 feeding cycles.
Once things start to go poorly with a true redtail baby your odds will get worse.