I bought this clam 6 months ago. It was doing fine but yesterday when i got home he;s fully open and not closing up. what could be wrong with it.His color is fine just isnt closing like he was any advice. have 300 watt metal hilides so its not the lighting or the water conditions. ammonia is o nitrates .05 nirites o calcium is 350 ph is 8.4 evryting else is ok. need help want to save this animal