Robins eggs

Hi, I’m new to this, I have a robins next in my shed, there were 4 eggs in it, I’ve watched the parents come and go, I’ve put robins food near so they can feast, I’ve been away for a few days and my husband has put food out for them but when I went to have a look today the food was still there, so I had a look in the nest and only two eggs, could it be that the other two have hatched and these have been left?