Childe's cooldown management is of utmost importance. Childe's skill can go under a long cooldown if you recklessly spam his melee attacks. The problem arises when you face enemies with Hydro aura that can apply slowing waters to your characters and increase their skills' cooldown. In those situations, if possible, it's better to clear a chamber in one go. If the enemies don't have massive health pools, you can easily wipe them out in a single run and avoid Childe's abilities' long cooldown.