You should jack your salinity up to about 1.025-1.026 as reefs do better at that level. Yours is VERY low...almost hyposalinity. Make the change over about 1 week.
It sounds like your tank is cycled. Especially since you used well cured rock. However, your nitrate is SKYYYYYYYYYYYYY high for a reef if they ever pop up to 25 ppm!! How can you say 0-25 ppm? That's a HUGE gap. This may be why your Xenia is choked. Nitrate should NEVER be higher than 10 ppm in a reef, but you should aim to be under 2 ppm, and as close to 0 as possible. 0 is achievable.
What are you running for filters? Protein skimmers? How big of waterchanges? How often?