I know from my years as a vintage textile dealer that you don’t want to store linens with starch in them. I think the starch breaks down fibers over time. I don’t think I would ever use starch on any museum linens at all, even while on display. There are ways to get the brown spots out (like Rit Rust Remover, soaking in denture cleaner, etc.), but I wouldn’t trust this chemistry on collection pieces. I’m guessing that there is a good reference source for basic textile conservation (maybe AASLH has one) that can help ground you in best practices. Good luck!
Ginny Daley, University of Kentucky