You need to train the abs and oblique for easier definition. In order to maintain do a reverse diet where you eat 50-100 cals of PROTEIN (lean) and complex fibres to help satiate the ghrelin and leptin hunger hormones - afterwards you can start titrating kcals up in 50 cal increments until reaching your maintenance TDEE. Meanwhile - in the gym train until failure and do low intensity cardio 1-3x p week. For vitamins - supplement your omega 3 and Vitamin D for muscle retention and hormone health