I don't think you have stray voltage..... Getting into sps successfully and especially acros seems to be the toughest for many reefers....myself, I've only ever run t5s so I have no experience with led. I have heard a few say that you need a decent amount of uv LEDs tho to have any success. As far as your parameters go, they look pretty good. I've never been able to read any nitrates in my water but 5ppm is not much.... Have you ever tested for potassium? I have found sps thrive when potassium levels are kept in check. Also, whenever keeping sps, pests or bugs always come to mind.... Do you dip everything? Are you sure you don't have any pests?
Some pics of the sps would be helpful too. You say that the tips go white first? But is the rest of the coral still coloured nicely with good polyp extension, etc??
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