Need help with father cockatiel attacks

Luka the tiel said:

WHAT IN THE HECK ARE YOU WAITING FOR?!?! SEPERATE THE FATHER FROM THE CHICKS AND LET THE MOTHHER TAKE CARE OF THEM! you will probably need handfeeding IF they survive after they lost blood inn such a young aga

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Been told it can’t be the father, happens at night so likely a rat getting to them.. Also been advised they are now too old to hand feed as been out of the nest over a week.
Had birds for over 30 years and never had this happen..
so far this summer 7 babies well , nest boxes taken down.
have been advised to put babies back as both parents have been feeding them…
Have made sure rats and mice unable to get in even though we haven’t seen any in the cage

Unfortunately our yellow baby died yesterday. My husband has made sure nothing can get in we hope..
Our aviary is quite large and we have in the passed had problems with mice but these have been very nasty to our lovely birds.
No more babies allowed for this year or next, it’s going to take a while to get over this..