your normal payment shouldn't change - is it your full payment that is due on the wednesday? or just the baby bonus installment

baby bonus is set to be fortnightly from when it is processed - so it doesn't necessarily coincide with your ftb. so if your first baby bonus and arrears hit your account on a thursday you would expect all baby bonus payments to hit on a thursday
for payment to be going through for the 11th, it sounds like you may have had a change in payday - it shouldn't have happened, but it may have been changed in the processing inadvertantly. if you'd prefer it to be on the monday, you can contact and have it changed back

i just checked online and it doesn't say what period you're being paid for, which is a pita - i could help clarify if it did!