If they are heritage poults, they won't really start putting on weight until after they are 6 months old.
#1 - Do not give them any mealworms!
Personally I am not impressed with Nutrena feeds.
If available put them on turkey grower. If not available, put them on Purina Flock Raiser or another quality All Flock feed. Meat bird feed is not appropriate for young turkeys. It does not have the proper levels of lysine, methionine or niacin.
Some people have good luck using fermented feeds. I do know that poultry will gobble up a wet feed and clean it up much better than a dry feed. I am not convinced that all the fantastic claims about using FF are true.
You can supplement their feed with vitamin B complex mixed at the rate of 1/2 capsule or tablet dissolved in one gallon of water. It should be the only source of water available and should be made fresh daily. It is good for all of your poultry.