Pink lines on stucco - help needed

Currently my guys are at this job. Washed this area as we normally do.

12.5% DS (with a little elemonator) with a 5.5 and thorough rinse - pink marks showed up after rinsing. Has never happened before and not sure what can be causing it. Was hoping one of you has had ran into this issue before and could weigh in.

Already arranged painters to come and paint but would still like to get a cause if possible.

Ask them what color the stucco use to be. It might be bleed through from previous paint.

Have you tried anything to fix it? Hotter mix? Oxalic? I’d probably give it a few days and see what happens when it dries. It might be one of those stains that just disappears on its own. If it is actually bleed through I doubt anything will fix it except the paint job.

Not bleed through; we got on the phone with the builder. Stucco is painted white - house is 5 years old. We tried stronger SH mix and F9 - the F9 actually lighten it up a bit but it was still pink.

Spoke to sherwin williams and they have no clue what it could be. The only thing I’ve read that makes sense is that there was iron deposit in the paint due to metal underneath and they had oxidized the paint - when bleach mixes in with those iron deposits it turns pink - kinda like with white t-shirts.

Would straight f9 work? If it’s iron F9 should clear it up.

I had a stucco wall do that, identical color…a big 4’ x 4’ place in the wall…by the next day it was gone. BTW, this wall was not painted…it was just the color in the stucco.

We tried f9 - it lighten up a bit but it was still pink.

Thanks, that would a best case scenario - I going to go take a look at it today again and see if hopefully we have the same luck. As of right now I’m paying for a paint job :confused: