He's on a med that's supposed to help his liver. I give him Serrepeptase (pain killer and anti-inflammatory from silk worm enzymes) twice a day, so 2 ml a day. I also give him acidophilus and electrolytes and have to give him lots of water & water on his greens. I'm making him swim every day, too, so he'll start using his legs again, he was hardly moving for awhile there. He's doing better in only a few days, sees the vet again on Jan 2. A friend of mine sent me a bottle of milk thistle liquid, that also helps detoxify livers, so helps alot with fatty liver disease. His kidneys are also affected, hoping the med will help with that. It's alot of work when they get sick.
Yes, small super worms will help them, they have more fat, so add weight, which is good for them. And continue feeding them separately, that will also help. Just make sure the super worms aren't adults, they're way too big for them. Smalls are perfect, just take out the biggest ones first, the smaller ones will then have a chance to grow. Get Wheat Bran as their substrate and feed them greens (on top of the Wheat Bran). It's the best substrate for them to live in. They can be kept in a small critter keeper or a container with a mesh top. They need LOTS of air so no mold starts. They die if they get wet.
Oh, I forgot to send you this link to good dubia roaches:
http://gordosfeederbugz.com/shop/feeder-bugs/dubia-roaches/
From checking other sites, she seems to have the best prices.
Hope you have a Merry Christmas and a great 2016. And if you get a 40 gallon, they can still share as it will be much bigger, space wise. Then later on you can get another 40 gallon and they'll have separate space. You can keep the tanks together, too, so they can see each other as they're used to each other, but that won't be for awhile, so we'll discuss it.