Need Expert Advice. Possible Metal Poisoning

Hey Guys. I need some advice on this one. Over the past month I have noticed severe bleaching on my greens birdnest colony. I have 3 large colonies placed in different locations in my 135 and all 3 have bleached almost white. Yellow polyps haven't opened up for a few weeks. All my leathers are not looking well and some brown polyps i have are not looking well either. On the other hand my 3 rose tip nems are all looking amazing along with my hairy mushrooms, gsp, pipe organ, frogspawn and waving hand. The tank is a 135 with a 40 sump. After checking all params and looking fine i started to look for signs of items that may have fallen in the sump or tank and possibly reaping some havok on my corals. I couldn't find anything but did a 40 gallon change last week. Today after things have not improved i started tearing thru my sump to see if I missed something. Well I found 3 sided 3 prong adapter in my sump. Im not sure of the metalic make up of this but im pretty sure there is probably copper in side of it. What stumps me though is the fact that some corals look great and the others just hanging on. My caulerpa and cheato in my sump are looking fine but the cyano i had in my display has vanished. Not a bad case of cyano but just enuff to irritate ones self. could this be the result of copper and it eradicated the cyano but was not yet at a high enuf level to harm the cheato or caulerpa. Anyways any advice would be appreciated. I gearing up for another large water change tomorrow but is there anything else i could do and am i correct in thinking this could be from this item that fell in my tank.

Thanks for listening and any advice is appreciated.