What starting dose did you use and have you increased it yet? When you mention good hydration how many ounces are you actually taking in? Also check that magnesium and potassium levels are adequate. Since you are missing your carb target most days try to bring those up because they matter for training even while on reta. Once those basics are covered watch how the body settles in over the next weeks.
I searched but found nothing so sorry if this repeats what others have said. I think the issue ties to the reta and hope this is the right spot. Second week in with the third shot due tomorrow. Trying to hit the gym more regularly now. Drinking plenty of water plus electrolyte drinks that worked for me during several Ironman races yet I still get tight abdominal cramps after just four crunches or sit-ups and can barely stand afterward. Nowhere else cramps up. Running a deficit around 1582 calories daily while aiming for 2200 but falling short. Protein stays high fat stays under target and carbs stay well under. Stats are 5 foot 10 male at 236 pounds with targets of 235 grams carbs 60 grams fat and 180 grams protein. Goal is recomp not only scale weight. Any thoughts on stopping the cramps?