You may notice an off-white residue and vinegar smell on your apparel. Don't worry! It's from a fixation agent applied during printing and it's not permanent.
Fixation agent (sometimes known as pre-treatment) is used for all DTG prints across the industry. It's needed so ink bonds with the fabric. Without it, ink would flake off the garment. You can think of it sort of like applying a primer before painting a wall.
The fixation agent can sometimes leave a faint square imprint around the print, and other small white marks on the garment. Your DTG apparel might also have a vinegar smell that gets stronger the longer it's in the poly bag packaging.
The solution is simply to wash the garment! Neither the residue nor the smell is permanent and both should go away after one wash.
If the discoloration is prominent, the quality control team will include a card explaining that it's from the fixation agent. Here's how it looks: