u r not getting weaker

let's do some really simple math in terms of projected one rep max

Weight x Reps x .0333 + Weight = Estimated 1RM (note : this does not work well beyond 15 rep range)

at 5 reps of 135lbs ur max will be approximately 157 lbs

at 12 reps of 115lbs ur max will be approximately 161lbs

technically speaking u r not getting any weaker, u are just over-thinking.

It ultimately boils down to what are your goals ? Choose ur battles -
more strength or merely chasing BIGGER numbers - then choose programs with lower rep ranges (<6 reps)

more hyperthrophy + strength (the best case scenario will be focusing more on compound movements to build strength and leave the accesory work/assistance work in higher rep ranges to either complement ur big lifts or work on your weak parts

sample

Compound loading movment

A1. Incline Bench Press - 4 sets of 6

Training density movement / assistance work

B1. DB Press - 4 sets of 10
B2. Cable flies - 3 sets of 15

There are a tons of to skin a cat. Choose ur battles and pick a program that reflects it and stop EMBRACING INTERNATIONAL BENCH PRESS DAY EVERY MONDAY.

Keep the magic three CHECKED as well

1. Training
2. Nutrition
3. Hormones (not necessary anabolic substances)

- Training includes recovery.
- Nutrition includes supplementation.
- Hormones includes everything related to your endocrine system.
- The magic three are inter-related. A change in one will cause a ripple effect to the other two
- be patient it takes time, u didn't get fat or stay skinny in 12 weeks.