My stack is very similar to yours, Stavia.
Recently I was also having stomach issues and thought it was just a bug. After it went on for several weeks, like you, I started wondering about all the supplements I'm now taking and how they might be interacting. As I think slacker also pointed out - our systems aren't static; things change. So, I took a day off from everything and immediately felt better. Starting from scratch is prob the best plan, but I just couldn't deal with that, so I added back the most basic ones that I started years ago and never had a problem with (in my case, the Meth B group, MagT, Ash, Mel, Citicholine). A week in that's gone well, so I'm now slowly adding in a couple more of the more important ones per day at lower doses. I'm holding off on my more recent additions (ALCAR, NAC, Ubiquinol, and Alpha Lipoic Acid), which are my prime suspects in the mix.
Some additional thoughts:
1) split the Omega 3 dose up
2) take curcumin w/food
3) If you're using Longevinex res, take a break from that as well, since it has multiple ingredients.
4) reduce methylfolate...thinking you aren't homozygous for MTHFR? Can't remember...
And let us know how you're doing? xo