please dont shoot me down but im gonna tell it like it is
your greys may look "healthy" now but who says in 2 yrs, 5 yrs or even 10 yrs time, nit-pickin at seeds wil keep em healthy
seed diets usually just allow the bird to pick out their favorite bits so therefor they arent getting a balanced diet so supplements wil then need to be given, and how do we know when we givin them the supplements they getting the right amount ??
at least with a pellet diet you know they getting al they need

plus unlike seeds, pellets have no waste

i guess its the difference between livin 15 or 50 yrs