Feeding young blue tits

Hi! Can anyone help?

We have blue tits just hatched in nest box.

The oak tree is late, heavy rain and I think a lack of caterpillars.

The parents are madly taking food from a coconut fat ball near the nest. I am concerned as RSPB suggests no fat due to chicks choking.

Should I remove it? What else can I give them?

Any experience welcomed. Thanks.