Making Changes
Don't.
The right movements will give you months and months of progress.
But if you're legitimately stuck, check these in order before changing anything:
Check 1
Time span perspective
After the first cycle, expect fewer PRs. Exercises will consolidate in performance sideways for 2-3 workouts before setting more PRs. They won't all do this at the same time so there's always something improving. Even a 5-10% total strength gain per cycle is mindblowing results spread across a year.
Check 2
Rest and recovery
Sometimes you just have a bad week. You're stressed, sleepless, sick or something else. Progress is never linear. When you're absolutely sure you aren't at your best, focus on beating your worst performances from before instead of your best. Raising the floor raises the ceiling.
Check 3
Bad technique
Most beginners and intermediates are bottlenecked by their form, and their form is always worse than they think. Technique improvements are the fastest way to make progress. Bar none. Common culprits: not setting scapula on bench press, swinging weight, partial range of motion, rushing warmups and feelers.
Check 4
Mobility issues
You're likely too stiff to actually do the exercise right. Do the 3 mobility drills more. Once you can move through full range of motion, the lifting maintains it on its own.
Check 5
Equipment and logistics
Home gym cables and bands can have inconsistent resistance. Use free weight and bodyweight when possible. In a commercial gym, different machines that do the same movement rarely match resistances the same.
Check 6
Bad for your body type
If all the above checks out, the movement might just not be for your body. People jump to this conclusion too soon, but it does happen. Try a grip width adjustment or a small swap. The right movement feels purely in the muscle with no weird joint torque.
"Hi/Lo" style for smaller movements
Smaller muscles need smaller jumps but most equipment can't go less than 5 lbs. For delt raises, biceps, and triceps, alternate a heavier week (10-20 reps) with a lighter week (10-15% less, 15-30 reps). Try to set PRs on both weights. Your heavy day slowly becomes your light day past 20 reps, then go up in weight.