If the increasing food noise is a problem towards the ends of your weeks then that is probably the primary reason behind your plateau/regain. You could switch to Reta which is generally more effective overall but it is weaker than Tirz when it comes to food noise specifically, so if you continue pinning once a week you may experience an even more significant issue in that area than you have been already. Whether you decide to switch or not I think the most helpful thing would be to start splitting your doses to smooth out the food noise roller coaster