The old saying in lifting is everything works, but nothing works forever. If you know your diet is locked in and you’ve taken an active rest/back-off week but seen no improvement (thus ruling out overtraining), fear not: there are a few different ways to bust through resistance training plateaus. One of the most effective in my experience is changing up your set and repetition parameters.
Have you been performing, say, 3 sets of 10-12 reps forever now? Try a cycle of 5 sets of 5 reps. Or 10 sets of 3 reps (one of my faves). Or even 2 sets of 25 reps. Test and find a weight that allows you to barely complete the given rep amount. Stick with the new parameters for a month or so, gradually increasing the weight each time you successfully reach your rep goal. When you return to your previous set and rep scheme, you should generally be able to work your way back up to where you were and then surpass the weight you’d been using. Booyah! Plateau busted.
Enjoy and lift well.