I don't hybridize, but I certainly do appreciate the time and energy that hybridizers put into breeding for rust resistance!
Here in Ohio, rust generally doesn't overwinter; but because I buy a lot of daylilies from southern sellers, I get it nearly every season. It's fascinating to see how quickly some daylilies look horrible, while others right next to them are barely affected.
Thank you for your diligence, and my sympathies on the death of your seedlings. Their sacrifice will not be in vain.