I am sure that the food you mentioned is nutritionally sound, but it is way too small. It would be like a human living off of supplements only. Your frogs need substance. You can pretty much use any aquatic turtle as a staple diet. Most people use Reptomin. You can find it at Petsmart and Walmart as well as just about any pet store in North America.
Tetra ReptoMin Floating Food Sticks - Sale - Fish - PetSmart You can also add yummy little things into your rotation as treats or occasional foods like store bought earthworms, frozen-thawed raw shrimp, scallops, talipia, salmon, and krill.
Is there any reason why you don't have all of the frogs in the same tank? They interact well with each other and would probably prefer the company. I am sure some may disagree, but that animal is suffering badly.
The frog in question, in my opinion is too far gone. I would put it out of it's misery and concentrate my efforts on fattening up the rest of your group.