I was flushing them in the past just when I was changing solution. And I change solution every 7-8 days.... So after 8 days I was flushing for a 1-2 hours, then added new mix....but again did not help so I stopt doing that.....a friend told me that is not nesecery to flush them because I change solution every week...but I´m open to try anything just to save my girls....one more thing, in veg stage they don´t show a signes of deficiencies.