Can I add 3 to 4 ghost shrimp to a Glofish/Danio/Neon tetra tank?

The ghost shrimp would work fine in the tank, but you are overstocked on the fish. Whatever you do, dont add more tetras. Even though they are small, it could kill the rest of your fish. Unless you have a serious canister filter filled with bio media, you bio filter is being overworked.