No real need to fear rejection on the part of the chicks. They are just "new" to the situation and need an adjustment period of a couple of days. Since they are so close in age, they should be very similar in size, and they will become a flock in no time at all. It's generally only an issue if there's a 3 week or more difference in age where there's a substantial size differential, or when you try and add new birds to an adult group. I'm sure everything will work itself out fine!
Congrats on the 2 new littles!
