If someone keeps CY as a chumra, I think it might still be consistent to not be makpid on formula if there was difficulty involved. But if CY formula is available at a cost differential similar to that of other dairy products, it would seem to me that there would not be grounds to be meikil purely based on the fact that the child is below the age of chinuch.
sorry, been really busy today.
Idk abt NY but WIC out of state only provides for the goyishe brands
(admittedly, when good start, soy formula was available we got it)