Are you saying the muscle pain and fatigue weren't there before the Lugol's? If they did just start after the iodine, that's a very strong reaction. If the salted water benefitted you for only 30 min, is it possible you're dehydrated? Are you drinking at least half your body weight in ounces of water each day? Is there any other information you could share?
Some people have this energized experience at the beginning of supplementation. Enjoy it. Usually it levels off after a time. But it leaves an indelible impression that whatever iodine is doing, it is good, and helps you want more of it even when you don't feel so hot. The good memories get you through the bad times.