We do not have the extreme heat as you, I never plant a daylily with the crown any deeper than one inch below the surface. I know when it gets hot here during July and August the daylilies will slow there blooming and sulk if they do not get enough water. I do not believe planting them deeper is the answer, if this is the first time it's happened I would leave them as they are and see if they bloom normal next year.
