We also have Pink on our ceiling, even though two separate techs have looked into the area above where it is pink have not seen any signs of water leaks and having set through numerous rain storms without any water coming in anywhere Forest River Warranty says it is due to water leaks ??. Another owner has a similar problem and his seems to be due to the seal on one AC unit not being installed properly, I will have my seal replaced soon.
So good luck on your pink ceiling and should you come to a solution I would be interested in your findings.
Pat & Gene