Rust stains on new plaster

[Blowout]

New 3m quarts plaster (Colorscape) has rust spots and streaks. Looks like what ever caused them was trowled into the plaster. They showed up right after filling and havent reduced in intensity over the past 3 weeks. The PB looked at it today and said a high a high acid startup will take them out. He tried pouring acid down a pipe to the stain and also tried a sanding block but the stain wasn't phased much.

I dove down and looked at the stains earlier with a mask and could not see any debris lodged in the plaster at least.

Not happy with stains on new plaster to say the least.

Any thoughts?
Thanks

 

[jblizzle]

Try rubbing a vitamin C tablet on the stains ... if it is infact a metal stain (likely this fast), then they should be lightened/removed.

 

[Blowout]

I'll give it a try this weekend...thanks