Weak chest help

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Hi /fit/
What should I do about my underdeveloped pecs?
Pic related. Pecs kind of like me but my delts, bis and tris are much bigger.
I ignored this problem before because I thought my pecs would just catch up later on, but now they're just disproportionately smaller. Q.Q
Also noticed I lack noticeably in pec strength. Can deadlift 160kg, squat a 120 but bench is just 60. And have been hovering around that mark for about 6 months. My workouts don't even feel like they're effective anymore, but if I bump up the weight I simply can't lift it. Doing 2-3 very heavy reps just doesn't feel very effective.
Tried SL 5x5 and I honestly just gained a lot of fat and strength went up very little.
I'm also probably a little stronger with dumbells.
My current routine
Bench 5x5
Incline dumbell 12x3
Flyes 15x3
Followed by tris
In terms of muscle soreness, all the rest of my muscles feel very sore after a workout but not my chest.
What am I doing wrong?