Firstly, you reached your goal. Bloody well done.
But afterwards the blues comes from both the adrenal drop of all the excitement being over and you having thoughts of "what now"?
I'd suggest staying as close to your routine and habits as possible. Yes, you should still train at the same time as you did during prep and make your meals the same. You should still be ticking your boxes daily like you did during prep.
Now it's time to set the next goal. Are you going to compete again this year? If so, then set the timeline for that show and see what work needs to be done in the meantime and get to it.
If not, then set a growth goal of what you'd like to gain and what you need to work on and get into the same rhythm you had during prep to reach that.
The only difference between prep and off-season should be the amount of calories you're eating and the amount of training/cardio you're doing. Your daily habits and routine shouldn't change. You're an athlete.
