You might be confusing cal def with lack of protein. If you are not consuming enough protein in your diet there is nothing to rebuild with meaning the damaged cells are returned to the body as fuel and not repaired, = loss of strength. Like I said the process of weight loss and muscle retention is the holy grail of body/strength training. You could use a visit to a dietitian who is versed in strength training.Is it normal to be about 10%-20% weaker on a daily 500 calorie deficit depending on the exercise? I lost 2 reps (used to be between 5-7 reps but now it's 3-5 reps with 185 lbs) on my bench press and I'm much weaker on my barbell rows (135 lbs feels like 165 lbs for the same reps).
Edit: I will be in need of one soon.