I think there is another route.. Doing things in revere for a period. Let me explain;I could pull a baby after a few days and hand raise him. I was hoping to get a friendly one anyway. I definitely don't want to lose any, so if that happens I'll try to help the little ones.
When you remove the significantly larger squab, to your warm home,,,, feed him the substitute feed. This way Lil Guy gets the premium stuff from mom and dad. Big Junior will be less demanding of parents to gobble up all the feed available.
I have never supplemented feed to my growing squabs. There are some peeps here that have. @Pyxis May have advice on stuff to purchase, and best way to do it