It doesn't have anything to do with your ink, but the dye in the tanks.
A lot of times, mills will re-dye other colors (unpopular or overstocked stuff that won't sell) black. I would contact the supplier and tell them you need blanks that aren't re-dyed since you'll be discharging.
A lot of times, mills will re-dye other colors (unpopular or overstocked stuff that won't sell) black. I would contact the supplier and tell them you need blanks that aren't re-dyed since you'll be discharging.