The point of having an appropriate starter (i.e. turkey starter) isn't to ensure fast growth, it's to ensure optimum growth, in other words, optimum health. Chicken starter doesn't provide enough protein, but if you're diligent with providing them with eggs, it's probably just as well. Just more work and expense for you, and you won't be sure they're getting all the other minerals they might need that could be different from a chick. I don't know a ton about poultry diets, but I do know that turkey poults sit around and dream up ways to die, so I like to be sure that I follow all the recommendations I can to make sure they don't die of something preventable by me. Good luck!