I'm not an expert on tulip diseases - it almost sounds like the Lilium could have a Botrytis infection but the Botrytis on tulips is specific to tulips. I would suggest you post in the "Bulbs" forum and see if anyone there can help you. If it's a specific tulip disease it wouldn't affect your other bulbs but if it's not specific then it could be a future problem (assuming it didn't originate in your home environment to start with).
If you post to the Bulbs forum, or we continue trying to help here, it would be useful if you could give us some idea where you are, doesn't have to be specific but diseases can differ from country to country and region to region. If you had a local extension office nearby such as in the USA then taking a plant there for diagnosis would be an option.