Naw, it sounds like you got yourself some good quality there. Naturally occurring l/r has pros and cons, just like cultured. My philosophy is, even if they say it's been cured, it hasn't. You must have some really healthy rock, a small amount of die-off is to be expected. At this point I'd continue with a one month q/t, I want a full month for EVERYTHING to q/t, I'm kinda "hardcore" that way. The patience almost always wins out, and I don't know anyone who would say it's not worth it.
Now, here's the thing: pests. You'll need to begin separating and observing the rock for pests (such as the ubiquitous Mantis shrimp) so you can isolate and remove before it gets into your system. The rock won't need light, but you might (to see with).
I, personally, would not worry about any phosphate or silicate leaching, unless you're testing for phosphorous and getting readings. As for silicate, that's an new area for me, so I can't advise you there. I think, however, that if you throw on a righteous protein skimmer you'd be golden. Otherwise, you're doing it pretty much the way I've always seen in done by commercial ops.