Have set up a new tank that cycled fishless for 3 weeks. Water was tested by 2 LFS and all clear. Added 6 Green Tiger Barbs, 6 Tiger Barbs a Red finnned Shark and a common Plec over 3 days. Carried out 20% water change after 3 days. All seems fine but the Barbs seem to be getting pale. Stripes on the Tigers getting faint and Green Tigers getting lighter. Behaviour seems OK has anyone else had this problem and what might it be?