YouTube's hottest fitness couple may be back on. Popular fitness personalities Nikki Blackketter and Christian Guzman shocked fans on Wednesday when they revealed that they had reunited five months after they had broken up. Blackketter announced the news to her 1.1 million Instagram followers, showing a shot of the buff couple on a beach in Hawaii, where they are currently vacationing together. "Whelp ... that escalated quickly," the bikini bodybuilder captioned the photo, adding, "#idontevenknow #explanationcoming #catsoutofthebag." Blackketter also shared glimpses of the pair's vacation on Snapchat on Wednesday, posting multiple selfies with Guzman. She also said she noticed that her back-on...