Be careful with stretch bolts, as someone else said tighten in the other bolts again.

I have drilled the head right off the stud in the past and when the stretch was removed from the bolt it just twisted out by fingers. BE VERY CAREFUL if doing this as when the head comes away from the stud it can fire off like a bullet due to the stretch in the bolt, I lost the head of a bolt completely once fuck knows where it went.