Sounds like your tank is not cycled.
A single uneaten shrimp is the same as a singe eaten shrimp, with the exception that most of the single uneaten shrimp is not generating ammonia and thus nitrites. That's because the best ammonia generators in a tank are the fish, not a piece of shrimp. The fish have the chemical process (digestion) needed to rapidly break down protein into ammonia. Not tank water.
Almost all of the ammonia in the tank comes from the gills of the fish, which in this case is to say, from the digested shrimp in the fish.
So yes, it makes perfect sense that if a load of protein (10-15 shrimp) were put into a partially cycled tank, and eaten (all but part of a single one) that nitrites would skyrocket and nitrates would be zero.
That pretty much is what every tank looks like at one point if it cycles from scratch,
Otherwise, I'm with Pops. It doesn't make a lot of sense.