Thanks for this reply. Let's see: stress, yes. Not enough water/fruit, yes. Overeating, yes. Eating without finishing digesting, yes. Eating too close to bedtime, yes. So even if I were lifelong vegan, I've had all those factors.
My question is more related to a meat-eater switching diet (all other factors being equal or slightly improved) so I guess as a meat-eater changing his diet, that may be a bigger noticeable improvement at first compared to a life-long vegan eating fried foods and having the above factors.
Basically I think I'll do what you say and make dietary adjustments. Whenever I have a healthily cooked heavy-vegetable-based meal, I almost instantly feel so much better, and my GB doesn't seem to complain at all about it, so I figure as everyone has said, this is an important path to healing.