Not that I am now, but I was one time ACE-certified, working out for the last 32 years. My recreational but competitive sports we’re running, orienteering, and rowing. Purely recreationally, I’ve done mostly fitness activities, and did bulk up in my early 30’s, mostly by not stopping lifting, but that said, over that time I’ve lifted inconsistently. Nowadays, my favorite activities are rowing (only on erg) and cross country skiing (mostly on the erg), spin, as well as some light basketball.
My thoughts about your issue:
- Routines need to change after thirteen weeks
- Rest periods for large muscle groups are 48 hours, but 24 for smaller ones. Thighs are big, calves are small, lat and chest are big, arms are small
For a change:
- Maybe you can do big days, small days instead
- You haven’t mentioned your rep range, but if you are using the usual 5 to 10, go heavy (3-5), or light(10-15), for 13 weeks
- Try working every set to failure, to momentary muscular fatigue (MMF)
- Try a periodicized routine, go heavy for 13 weeks, go bulk for 13, and try fast/light for 13
- Use different weight types and/or machines
Much of what I’ve mentioned has been suggested, proven, and sometimes disproven, but it seems like you need to change.