Birds have disappeared after a few days without food

We have been on holiday for a week. We filled all our bird feeders the day we left (Fri 2nd) so there was enough food for about four days for all our sparrows, blue tits, starlings and rooks. We came back on Fri 9th and filled all the feeders but none of the sparrows or blue tits have come back. The starlings and rooks ate the meal worms immediately, but all the little bird feeders have not been touched. We have so enjoyed getting into feeding our birds, have I lost them? Or is it something to do with the hot weather? Thanks