First, have you handled them alot, or have you let them adjust to their new homes? Stress will make a new baby go off their food. Leave them alone, except to check their water and such, trying not to disturb them at all. Give them at least 4 days between trying to feed. The next time you try, as you said, brain the pink, or pop a head off of one, and put the food item and your little snake in the deli cup you got them in. If you didn't get them in a deli cup then find a small container that size and poke some holes for air. You can place them back in the cage in the cup and leave them totally alone all night. (If you do this before bed it is easier to leave them alone) In the morning, hopefully, the pink or the head will be gone and your snake will have a nice little lump. You may have to do this more than once, since sometimes it can take a few times.
If this doesn't work, there are many other things to try. You can wash the pink, to make it smell less like a pink, scent with tuna water, anoles, other small lizards...etc.
Don't give up....sometimes you have to do some really not to pleasant things to get a little one to eat.
GOOD LUCK!!!!!