As has been mentioned, some deaths can almost be expected in a large group of chicks, that is why the hatcheries normally add some "peanuts" to the orders. Did you have any stressed, sick, or dead chicks upon receiving them?
If you're seeing most of them eating and drinking then the other chicks are pretty well doing the same. As for the crop, it should not feel like it has a hard ball in it, it should be pliable...imagine a small bag of feed that has been moistened. If the chick eats too many shavings they fill the crop and will not pass on through the gizzard, this causes an impacted crop. An impacted crop is full of non-passable material that will basically starve the chicken (no nurishment gets through), it can also "go bad" while sitting in the crop and cause bacterial infection problems.
Chicks will peck at anything and everything. For the first several days they have no idea what is food and what isn't. If they can get it in there mouth they will most likely swallow it. Thus, the reason for covering the shavings with paper towels. It doesn't take the chicks long to figure out what the food is but those few days can be dangerous for them. Long pieces of "hay" also have somewhat of a reputation for causing impacted crops in adult chickens.
I would just try to feel each one's crop and see if one or two feel "different" (as in harder) from the others...this could be what is happening. It could also just be the mortality rate of this batch of chicks that you are experiencing. It appears that several responders here have not had the best of results from MM Hatchery. But, I would imagine there are folks in the forum that have also had good results.
So how are they doing this morning?
Ed