Meryl's bird box

Hi. Ours we think has laid a 5th egg this morning although she has covered them up so can't see clearly. She is out of the nest and hasn't been back which suggests she hasn't finished laying. We see the parents regularly on the feeder and can hear the fledgies in the yew tree and can see the parents flying with mealworms to them but they are too high up to see. I bang the plastic box when I put the mealworms out and they all seem to realise and then we get a flurry of action from the robins (who have 2 fledgies we've seen) and several other pairs of blue tits and another great tit pair which our male tries to drive off the feeder. I am debating whether to continue with the larger mealworms and order more as I don't them to start trying to find food further afield and forget about our feeder. An expensive business though..and double trouble this year it seems!