Hello and welcome to BYC! Glad you joined.
I hope you've reinforced your coop since the attacks to make sure nothing gets at them again.
I introduced 3 full grown pullets to my flock of 9 but did a pseudo-quarantine. I had coccidiosis rear it's ugly head but because I was watching for signs, only one bird ever showed any illness and it was for just a single day. Keep an eye out for that for the first month after introductions as well as any other diseases or parasitic infestations, internal or external.
Welcome to Backyard Chickens! We are glad you joined the flock! BYC is a helpful site providing all of the information you need to know about poultry. There is always space for members on the BYC roost!
Integration definitely can affect egg laying conditions and cause the pecking order to be more extreme. The whole flock is unsure of their position in the pecking order and hens who are more bullied will also tend to take a break in egg production.