Mine are very finicky too. I have also tried tons of different foods. Right now I have a mixer of Purian One, Pro plan, UltraMix, Canidae all dry.....
They seem fine on this ... for now
I free feed as well. Sometimes Cody will go 2-3 days without eating. He just nibbles here and there. Sometimes I have to fill his dish each day. Just depends. I personally think they are NOT going to starve themselves, JMO.
When they are hungry if it is out they will eat. JMO though.
Good luck. If your baby isn't acting sick then don't worry about it. If you are worried then give her/him some nutracal.
