Another possibility: if the supplier was keeping the newts terrestrial, it may take some time to re-adapt them to water. Is there a way to lower the water level in the tank?
When I need to adapt a terrestrial newt to water, I put it into a shallow (about 1 inch of water) tank with a few flat floating islands. The newts can sit on the islands, but they stay somewhat wet even when beached. The trick is to have enough islands that they can stay on land, but keep their skin wet. Usually within a few days they are acclimated to water; their skin is wetted and they become less intent upon staying on land. A newt that has been kept terrestrially will cling stubbornly to land until its skin adapts, and it will never adapt if it's not kept wet.
