I had a similar problem.  All parameters seemed OK but I was using a float style salintiy test.  When I measured with a refractometer I found that I was up around 1028-1029.  Once I brought it down everthing came back and the corals overgrew the algae tips. 
 
Joe 
		
	
		
		
		
		
			
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				210 Gallon slowly gaining population. 
 
Foxface, Naso, Coral Beauty, 2 Clowns, 2 Chromis, Orange Anthias, and Striped Goby.
			 
		
		
		
		
	
		
		
	
	
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