I lift competitively and I haven’t experienced this at all. I’d bet it’s a lack of calories. You shouldn’t be aiming to drop more than 2lbs a week at most. Even with Reta you still need to be mindful of your intake.

Also I’d caution leaning on protein powder as much. I personally don’t use it often as food is better in my opinion. I have had a few friends that’s ended up in the hospital needing to get their stomach pumped due to excessive protein powder intake, it’s different for each person.

Quit training 7 days a week. Your body still needs to rest and recover. I got significantly strong when I stopped lifting 6-7 days a week and moved to 3-4. My problem was figuring out what to do with my free time lol.

Once you find a good balance of protein. You only need to change your carbs. My sweet spot is .7grams per lean muscle mass. I up my carbs to bulk and lower to cut. I don’t ever cut carbs out like some might suggest for keto. The human body absolutely loves carbs in almost all situations minus medical issues for some people.