nesting blue tits

Hi,  I have blue tits beginning to nest in my garden nest-box. They have nested here for many years but not last year.   In the past I have had fatalities in the box, although some in the box at the same time have flown.  But the year before last  I found 6 dead ones and only one surviver.   I have a peanut feeder about 10feet from the nest and I noticed that the parents were feeding at the nuts and taking it to the nest.  I am wondering if the little ones got choked on the peanuts.  There doesn' t appear to be any thing else that would cause it.  Do you think I should stop feeding them when there are young ones in the nest?     Many thanks.    Byegeorge