if  you added coral within the last month then it could have come on that in a dormant stage and then hatched in your tank. 
that is very odd because there is no way that marine velvet would have been in your tank for 2 years without wiping it out. 
Marine Velvet is horrible and brutally efficient at wiping out complete tanks in a very very short period of time. 
other than that, I have no explaination. 
		
	
		
		
		
		
			
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				Way too much time and money has gone into this hobby....and yet, I CAN'T STOP
			 
		
		
		
		
	
		
		
	
	
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