How do you overcome plateaus

I've been training for less than 6 months, I think around 4-5 months and I go to the gym, and I have noticed that my hammer curls have plateaued, I do full rom standing hammer curls, and I remember the highest amount of reps i got was 10 reps, but after that it would drop to 7 or even 6, then it would climb up to 8 to 9 then drop back again, It's been stuck like this and I haven't gotten past 10 reps, I once hit 10 last time but then my reps dropped again. Do I need to switch exercises for backpressure or am I just lacking in rest or nutrition? I am maintaining 75kg and I usually get a good amount of sleep although I haven't always been consistent with the gym, other exercises have not been affected like cupping, pronation, rising, and sidepressure but only specifically my backpressure.