You may just find it was a poorly spawn hun.
In theory at 3 months they should all be eating powdered adult foods and micropellets with some of the bigger ones starting to manage adult pellets.
Live food will always give you the best growth rate so I'd use it until you get them to size then worry about weaning and fussy eaters
at the current size trying them on non live food they are more likley to get weaker and thiner with refusing to eat it.
In theory at 3 months they should all be eating powdered adult foods and micropellets with some of the bigger ones starting to manage adult pellets.
Live food will always give you the best growth rate so I'd use it until you get them to size then worry about weaning and fussy eaters
at the current size trying them on non live food they are more likley to get weaker and thiner with refusing to eat it.