Hello and welcome to TFP!
When I saw this post yesterday, my jaw hit the floor. That's a lot of discoloration following a recent re-plaster job. What worries me are the unknowns to this point, but I'll ask you some questions to see if it helps give us a better picture of what happened and/or if anything can be done to improve your situation:
- "Kept chemistry good." Please tell us how the water was tested (local store, yourself w/ what test kit?)
- What start-up process was used once the pool was refilled? Do you know?
- What have your plaster contractors said? Is there any warranty period?
- Who winterized your pool, and what products were used (chemically) to treat the water when closing for the winter (anti-freeze, algaecides, etc? - what kinds?)
- How did you test for copper?
That laundry list of questions should kick off a decent dialog by which we hope to get you some answers. Thanks for using the forum.