Have you tried any periodisation?
I don't know what the rest of your workout schedule is like but I'll try and give a brief example:
Let's say you are stuck at 50kg for 5 reps on the incline bench. Since you can do well over 80kgx5 on pulldowns/pullups and over 100kgx5 on the squat, we can assume that you have the ability to lift more on this exercise.
Week 1:Start the particular day you are doing chest (or if full body, everytime) with inclines and do, as a max effort, 30 kg for 5 reps. No more. Keep doing the other exercises but not to your full capacity. Save your strength.
Week 2:The same but up the weight to 35kg for 5 reps.
Week 3:Up the weight to 40kg for 5 reps
Week 4:Up the weight to 45kg for 5 reps
Week 5:This is where you'll know how well the cycle has worked (if it hasn't, perhaps your diet/rest need attention). Up the weight to 50kg for 5 reps.
Week 6:Up the weight to 52.5-55kg for 5 reps.
If the cycle keeps working, by all means keep adding the weight.
Best of luck!
