Hi and welcome to the forum.
It's obviously the lack of bowel movement. Any weight gained over only 3 days is either water or gut contents. Weight loss is almost never linear. Just stay on track and the results will come. Also, going super-low carb isn't strictly necessary. Some people do better with lower carbs and some do better with higher.
Two hours a day in the gym is a lot. Is this every single day? If so, I'd cut back. A lot. It is too much stress and might be causing elevated cortisol levels. Have a short, intense workout and get out of there. Then go for a walk or do something else relaxing.
I wish you and your wife the best of luck!