Find out what your friend was doing different than you. Thriving for a week doesn`t mean success in this hobby. I`m not trying to be a dick, if I come across that way it is not intentional.
http://www.wetwebmedia.com/featherfdgfaqs.htm Check out this thread it`s long, and I didn`t read it all but you should get some good info from it.
How bad did the shell crack, is it possible that a piece of the shell is sharp and irritating the worm when he extends. Mine have also been known to get a bit grouchy when I move them and won`t extend alot until they acclimate to their new spot in the tank. They like lots of flow. You could try some phyto or other filter feeder foods in the tank, but they probably are not necessary. If you are going to try feeding use TINY amounts a 10 gal tank can go south on you very rapidly.