My newt was like that, you need some changes.
First of all is your filter producing a very strong current? If it's too strong the newts may have went in the water, and if the current is too strong for them to swim to the surface they wont go in the water. Remember they must come to the surface to breathe air. I suggest keeping the filter, if you have gravel you'll need to clean that with a gravel vacuum.
Also you must make sure the water is clean and has no chlorine in it.
Can they get on land easily?
The heater HAS to go, they dont need it and it's bad for them, and it turns out sunlight is bad for them too, keep the tank away from direct sunlight and heaters in your house! You dont need a light either unless you want to see them for a few minutes.
The frog has to have its own tank, newts and the frog require different things, and the newts can be toxic to the frog. Is it a land frog or water frog (clawed frog)? Water frogs will over-eat themselves to death, they will compete with the newts for food as you may have found out. Just setup a tank like you have now minus the land because water frogs dont come out on land.
Now for food.
Your newts wont go in the water for some reason, but they usually love the water. I would feed them every 2 days until they both eat each time, they need to fatten up so offer more food until they have no more problem eating.
My newt will only eat under the water, but newts will eat pinhead crickets on land.
All other food is eaten under water, so you'll need to put food in the water.
You need to put live worms in the water if your newts are in the water. I would try live blackworms, they are cleaner than tubifex worms. Put a toothpick full of them in front of the newts face when they are in the water, but let the worms crawl on their own dont hold the toothpick in front of them it may scare them,they should snap them up quickly once they see the worms crawling.
I feed mine a small earthworm whole, the length of it's body, and the width of the worm about the width of a toothpick. My newt eats a whole worm every 2 days.
Remove any uneaten food after a few minutes.
Hope that helps.