need expert advice:caulking around tub
We had our kids' bathroom remodeled a few years back, and after about a year, I noticed the caulk around the edge of the tub (where it meets the tile walls) was slightly gray in a few spots. This was not on the surface, and no mildew cleaner faded it at all. It spread gradually, so eventually I had the guy who'd done the tile work come back and replace the caulking. However, now it's a year later and the caulking not only has a few light gray areas again, all of the caulk seems yellowed, and there are cracks within the caulk itself. The yellowed caulk against my white tile looks pretty bad, and now the edges of those cracks are discoloring (rusty) even further. This obviously got away from me (and apparently the cleaning lady wasn't doing much of a job, but that's another story). My old caulk before the remodel was never this much trouble.
Clearly I need to replace the caulk again, but I do not want this to happen again, so I need to understand what's wrong! A little investigation online points to two possible problems: 1) the wrong caulk was used. and 2) chlorine-bleach products made the caulk yellow. Perhaps the problem is a combo of these two. I don't know about the gray--maybe mildew on the underside if things somehow didn't get dried properly before the work?
So, does it sound like the wrong caulk was used? And can products such as Clorox yellow the caulk? Is that true even if I replace with the "right" caulk? Lastly, DH and I have little to no experience w/caulking. How hard is this to get right for an amateur? I don't want to call the tile guy back since that got me nowhere before, but I'm a little reluctant to undertake the job. Help!