Thank you @roseseek! I’m sorry to hear the HdB seedlings were so sick. Rust hasn’t been a problem here but I definitely will keep an eye out for mildew.
Unfortunately the older posts on this forum show up as "Anonymous " so I can’t tell who posted it, but one of the mentions of seedlings inheriting stripes from them was here:
(I hope that link works!)
Unfortunately, I have no idea who that was, and they didn’t provide any further details.