Have you tried giving them just cut up fruits and veggies? My gliders prefer to have little glider hand size pieces they can pick up and carry to their favorite spot to eat.
If I give them pureed fruits or veggies or baby foods, they eat about 1/4 of it at best.
My GliderKids do not seem to care if their fruits or veggies are fresh or frozen. Frozen ones have thawed to room temperature by the time the GliderKids wake up and are ready to eat them.