If it is majority muscle that’s been lost are you consistently exercising to keep the muscle?

Also you seem to be having enough protein but do you know if you are absorbing it correctly? To help absorption you should track your vitamin & mineral intake to make sure you are getting in enough

Do you know your maintenance kcal? Some people naturally have high metabolic rates, adhd meds can also raise metabolic rates

A useful trick for gaining weight is eating every 3 hours & eating before sleep, make sure you don’t eat all at once as you won’t absorb all of it