Get some ROX carbon from BRS. BRS is really the only place you can get it from and trust me once you go ROX there is no other you'll go to afterward. I only wish some of our more local vendors would bring it in (HINT HINT ... er, AGAIN, because it's not like I haven't brought this up before).
But Doug is right, get some carbon on there. It's mandatory IMO. Read this for a good description of "why":
http://joejaworski.wordpress.com/200...k-need-carbon/
Doug is probably also right in that the reason for your SPS troubles are your leathers. In general these two types do not mix well at all. With maybe only a few exceptions you don't really find SPS and leathers in the same reefs in the wild and that probably tells us something.
And it's not just leathers. Softeys in general, macro algaes, leathers are just among the stronger one who participate in allelopathy ("chemical warfare").
You can mitigate this some by using more carbon but there will be a point where it's sometimes better to pick your favourite kinds and focus on that for a single tank. There are not many "mixed coral garden" that last very long and it is because there are just too many interactions going on that we can't really see or do much about.
But yeah, I agree. Start with some carbon and go from there. (See if you can get the ROX
http://www.bulkreefsupply.com/store/...-carbon-1.html ... well worth it.)