I didn't see you mention what type of salt you are using...have you recently opened a new bucket?  There can be other extenuating factors...not saying just salt but its something to consider. 
		
	
		
		
		
		
			
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				Mark...
  
290g Peninsula Display, 425g total volume.  Setup Jan 2013.
			  
		
		
		
		
	
		
		
	
	
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