How to correct dogs who only misbehave at night?

I have 2 Labrador Retrievers that are just over 2 years old. During the day, they don't really cause any trouble at all. However in quite a few mornings it's quite obvious that during the late night when everyone was asleep, they got into some mischief. For example, they may have chewed up a water hose or torn branches off of plants, or destroyed a cushion. The worst part about it is that they know it's wrong already because whenever I go out in morning, if I go anywhere near something that they destroyed, they lower their heads and slowly walk to me and try to shake their paw, or they'll just slowly creep away, before I even say a single word. So it's very obvious that they know they're doing wrong and they intentionally wait until we're all asleep to do wrong. I'm not sure how to correct this behavior if I can never catch them in the act. Any ideas?