I would say off hand that it may be your lights. 150W is marginal for a 30" deep tank. Are the corals near the surface doing better than the deeper ones? I know some of my acro's near the bottom of my 24" tank need to be moved higher, and i am running 250W 14k Phoenix bulbs.
Stray voltage should be 1 probe in the ground pin of a socket and 1 probe in the tank and then check for DC voltage. Lots of people report some stray voltage with no effects on thier tank tho.
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