I am Plan F and have hypothyroid (prob Hashimoto's) and RA. I am taking T-100 by Dynamic Nutritional A. as per my ND, which also contains plant cellulose, vegetable stearate, magnesium stearate, and silicon dioxide. Would it be better to take Ashwagandha?

Continue your thyroid support as your ND suggests. Ashwagandha is a nightshade. However, it's also one of the most nourishing herbs on the planet for both the thyroid and the adrenals. I would not worry at all about the ashwa in the formulas. If anything, it will support your nervous and glandular system and have you needing less thyroid support. Of course, if you react to it, that is a different story.