You can do either…
$qb->where('e.fecha BETWEEN :monday AND :sunday')
->setParameter('monday', $monday->format('Y-m-d'))
->setParameter('sunday', $sunday->format('Y-m-d'));
or…
$qb->where('e.fecha > :monday')
->andWhere('e.fecha < :sunday')
->setParameter('monday', $monday->format('Y-m-d'))
->setParameter('sunday', $sunday->format('Y-m-d'));