I've always taken a lot of supps, so couldn't say anything was different.
Never had any tests but can pinpoint the onset of my symptoms to a perfect storm of mercury toxicity. Had 6 Amalgams removed unsafely (and swallowed a huge chunk of one) after years of night grinding, ate tuna sushi 3 times/week and lived on canned tuna when I was in college.
I did begin a candida battle just before starting chelation before learning not only that my symptoms were mercury-related but that candida is mercury-related as well. Those were dark days, with me on a Saturday night staring at the probiotics in the Whole Foods cooler like a jonesing junkie :-)
I think a big part of my chelation woes were because of candida die-off. But the mercury moving out didn't help as I understand it paralyzes the intestinal tract on its way out (my stomach would feel like it just stopped digestion). Not to mention the disheartening drop in body temp, debilitating fatigue, difficulty breathing and all the other maladies I encountered as mercury did its conga line out of the system.
I alternated several treatments, taking breaks of a week or so in between. Chlorella/Cilantro, ALA and NAC, all with vit C, sulfur foods, Iodine and MSM.
Feeling better on my weeks off would lead me to jump in hard with chelators until I finally got the message that laying on the couch feeling horrible was probably not the sanest route. Now I steel myself for a round but the combination of slow and go and the fact that my load seems much lower makes the process a lot easier.