For a tiling job, I used this charcoal grout:
After a few days, as indicated by the instructions, I applied this sealer:
A few minutes after applying the sealant, these white stains appeared randomly in the grout:
It's been a few days and the stains are still there. What should I do about them? They tend to vanish if I scrub the grout, but I'm not sure that's what I'm supposed to do.