The tank is actually better than i expected but it definitely has some issues. You shold get rid of the filter, it's not helping. You don't need it at all in a large tank like that, specially with plenty of live plants. It's entirely redundant and all it's doing is create some heat and an undesirable current. The newts will apreciate the water being completely still. You should also add plenty more plants. Ideally you want the surface to be covered by a thick layer of vegetation so that the newts can stand on top of it with their heads sticking out.
I would also recommend reducing the amount of light, it seems to be rather excessive. You could perhaps suspend the light a bit further over the tank to reduce the intensity but also to allow for much better ventilation. As it is, the lid covers so much of the surface that i expect it is heating the tank significantly. You'd be better off with a mess lid that neatly and tightly fits the entire top.
These newts should be 100% aquatic in captivity, so the fact that yours aren't, coupled with the fact that they are thin and not in good shape is an excellent indicator that things are not right. You need to work towards getting them to eat consistently (and only good, nutritious foods like earthworms) and to make the water comfortable for them. That will give them a chance. Like Chinadog said, many such newts die shortly after being purchased, most of them from flesh eating infections which develop because their inmune systems have been nullified by stress and terrible conditions. That's why it is imperative that you offer as optimal conditions as possible now.
In the future, if you acquire more animals i strongly recommend not to purchase WC animals from shops, it is a terrible market that causes a lot of death and missery. You have plenty of captive bred alternatives that are much more ethical and make much better choices as a costumer as you will be getting healthy animals.