Purina does have a 30% Gamebird starter, but Purina flock raiser is only 20%. It is ok to feed this to your mixed flock as adults but turkey poults have more needs out to 8 to 12 weeks.
Thought you said you were feeding this, it is 20% protein.
How are you handling the different temperature needs in brooder for this large age/temp differences? I would not brood your turkeys with your chicks as it can cause problems for your chickens later on. What variety of turkeys are you...
Turkey poults need a much higher protein % than flock raiser, that would be ok as adults. As poults they need a turkey/gamebird starter around 28% protein. And the turkey/gamebird starter is much higher in Methionine and lysine which turkey poults also need. Don't believe that is your problem...