DLE Lupus skin disorder

My 12 yr old beardie has lupus, been fed dry food ( lifestages salmon/trout grain free). She has gained weight through steroid use although not on them any longer. I am looking at different diets but want to give her the best nutrition for her auto immune condition, high/low protein, low fat, dry, cold pressed, etc.
She is on doxycycline and niacinamide and its working quite well for her skin.
She has been spayed and weighs 27kgs so im looking to get her weight down.
Any advice will be appreciated.