Without a picture we can only speculate. I would think the spiderwebs are either a type of sponge, which is nice, or a vermetid worm...also a good thing. They may look kind of messy, but they are beneficial. The white stuff...well, we need a pic, it could be white coralline algae, which either means its dead coralline or new growth. Either way all of these things sound normal. Did I mention you should post a picture?