Female wont let the male in the nestbox!

[featherlove]

I have a pair of cockatiels that have been together for over a year. This year I decided to open the box up for them to breed. The first clutch of eggs were no good and she got off them and let them go cold, so removed them.. This next clutch of about six eggs, two days ago, one hatched.. Much to my delight. I was so happy for them both.. very proud ..
The first couple of days, mum would let dad in the box during the day, and it seemed they were sharing the duties of looking after baby. This morning I noticed two more babies hatched. Oh wow.. lots of delight and cheer.. I was talking to the male as i was feeding the budgies on the opposite side and heard the female getting angry.. i turned to see the male shooting out of the nestbox lol.. he was out of there .. zooom! It appears that the female today wont let him in. Is this because there are two new babies and shes just being a protective mum? or is something more sinister going on.
This pair are right next to my back sliding door underneath my patio area so I can hear them all the time. They are very well supervised. I will be keeping my eye on them.. and I do baby checks of all my parents morning and late afternoon .. Just wondered if anyone had any advice ..

[featherlove]

update:
All seems well.. mum and dad are sharing the load of the little ones,.. they are loving the celery and greens i feed them, and feeding them to their bubs seems like the summer thing for these guys.. dad is allowed in the box now, and feeds the two babies. .one has eyes open and is so cute as he hisses at me .. the other has eyes closed still but is definitely growing ( he is only four days old) ..
I guess it just takes a while for them all to settle into a routine, just like any pair.. and really just like humans!