I have found that hot weather makes them sleep more. Doesn’t matter if they are inside where it’s air conditioned.

Rabbits are sensitive to light. Light inhibits melatonin, the sleep hormone, so less light makes them less active.

They also get less active when its hot, during the day. A sprawled out resting bun doesnt generate so much body heat (muscular work raises body temperature), plus the bigger surface area makes heat disperse more readily.

Humans function much the same way, we sleep more during winter. When it’s hot we generally dont feel like doing much, although we have the advantage of being able to thermoregulate by sweating. Rabbits mostly rely on their big ears for thermoregulation.

As long as your buns’ appetite is good and their poop is good, I think this is fully normal.