This happens with alot of exotic species. They often have trouble with crickets (wahlbergii especially), and sometimes wax moths. It is tough for them to get over it, but next time try feeding them flies that have been fed sugar. I do not know why, but that seems to work great. They will continue to puke over the next couple days, but after that they seem to do fine. Clean/change the container everyday if possible, or at least every few days until the puking stops.
I use to have this problem alot until I realized it wasn't necessarily the crickets, but the diet the crickets were on. I have stopped feeding any of my feeder bugs carrots, as I noticed the mantids puked when I gave them roaches that were fed carrots earlier that day. That was the only time I EVER gave my roaches carrots (I was out of apples!), and the only time I have EVER had a mantid puke from eating a roach. I feed my mantids crickets now without worrying, even the wahlbergii.