When your juice starts loosing flavor its usually time to change the coil or if you strt getting a lot of spitback/spatter when you take a puff it it could mean the coil is getting gunked up and needs to be changed
Ok I thought maybe your coil was starting to burn But if flavor is good that's not it Im stumped on this Im sure someone who is familiar with that mod will chime in and help. Sorry I couldn't
I vape mostly dessert type juices if they start loosing their flavor I will vape some fruity juices for a bit that seems to help me get my taste back for the dessert flavors