Not really.They should be mature enough to lay rn at 4 months as Wyandottes.
Photos would be very helpful. 4 months is pretty young. Maybe a Leghorn or production pullet may lay at that age.
I'm sorry that a dog attacked the flock. Hopefully they just scattered and you will find them. It would be a good idea to look over all the ones that you have for wounds. If any of the missing return, check them out really well too.