if light were the cause of potent plants we'd all be boosting our lumens...but it doesn't work that way. i had a power failure last winter and lights went out and didn't come back on for who knows how long during flowering (was away for several weeks and used a digital timer that resets when power is cut) and harvested them when i returned. noticed no diff from a previous harvest of same bb strain. i wouldn't make it a habit but i'm positive 48 hours of darkness will do them no harm. some people even put them into total darkness the last days of their lives...also clones get sent around the world and their time in darkness is far longer than what you have planned.

no worries and good luck