Answer: Generally speaking, the Cooperative Extension Service is a great resource for help caring for plants given your local conditions. In Alaska, they offer an Ask an Expert service covering a variety of subjects, including gardening. See: http://www.uaf.edu/ces/info/askexpert/
However, I didn't find any information on this topic already published on their website. From what I've seen on other sites, Oriental Lilies normally die back once they've bloomed, so losing leaves may be a normal part of the plant cycle. There are many free sites available that provide a wealth of information on caring for Oriental Lilies. I recommend using your favorite internet search engine with the terms: <"oriental lily"> and
"oriental lily" plants care
If you want to avoid commercial sites, with loads of advertising, try limiting the search to educational or governmental sites by adding either site