Colloidal Silver kills ALL dandruff on contact and it will take a good 3 months to return. So apply Colloidal Silver to the scalp & beard about 4 x per year or as required. This treatment for dandruff sometimes lasts much longer.
Sadly, lab results that are "in range" will not necessarily support optimal health. Those ranges include the results of people who are very ill.
You could be right about your adrenals having taken a hit. Salt is their friend. Consider trying 1/2 tsp pink salt today, and at least 2 quarts of water. A quarter teaspoon per quart might help revive you. A sodium result of 139 6 months ago could be worse by now, or at least not much improved.
Sounds like you may not have had the companion supplements in place before you started Lugol's. Vitamin C and B vitamins come to mind in particular right now. Start some salted water, both drinking and gargling with it.