You've stalled. Simple as that, happens for every lift at some point.
- Drop your TM back 2-3 cycles, so 20-30lbs depending on your increment
- Change your assitance up if they've been the same for awhile
- Try some programmed progression to your assitance e.g. SST or 5's PRO, or just do 5x10 then 5x8 then 5x6 instead of the same sets/reps repeatedly.