Losing all my lps corals, what's going wrong?

[GoldenFusion]

Hey all, I'm having some issues with my Lps. Over the past month or so, I've noticed they're receding, mainly on the hammers in one of my tanks. I've got another display and a frag tank on the same system, but it's just the hammers that are giving me trouble. They're not opening as much day by day, and now they're not opening at all. Same thing's happening with my Zoas - they stop opening, then just vanish. Any advice would be great, thanks.