Wet cardboard on off white carpet...now pink...PH??

[Goomer]

Customer just moved into a new apartment and had all their stuff boxed. A sink somehow overflowed tap water while they were not home, and soaked several rooms. Every box that was wet, left one of these pinkish stains....

Wet boxes sat for about 24 hours. What appears to be a clean strip through the middle, is where the boxes were taped, and the cardboard did not come into contact with the carpet.
Water clawed and cleaned, but barely lightened them.
The only thing I was thinking it could be was a PH issue, but I have never dealt with one before, and did not want to do anything else to try to fix it that I could not undo.

So what think you???

 

[Royal Man]

Is it an imprint from color on the boxes?

 

[Goomer]

I checked the bottoms for the orange HD logo, or anything else, but bottoms are plain brown cardboard with no print on them.

 

[Royal Man]

When PH goes pink. I go base instead of acid.

Test a small spot with baking soda or ammonia.

You may have to cover with plastic and let it dwell for 24 hours.