a danger of having multiple supplements in liquid drop form

I put what I thought was 6 drops of Vitamin D on my spoon, put it in my mouth and started swallowing it. The taste was unexpected; strong and sweet instead of mild and oily. Realizing it was iodine drops instead of Vitamin D, I spit out as much as possible into the sink. I don't want to overdose on iodine. Per that article, 6 drops would still have been under the recommended upper limit, but it would have been half-way there.

I don't take either of those supplements on a frequent or regular basis; I also take chewable children's multivitamins. Both bottles are quite old; I suspect the D may have lost potency so I'm less worried about taking more of it. But iodine is a mineral which I imagine is less likely to lose potency, and its dosage is a single drop per day to get 100% of the recommended amount.

Most people don't need to supplement with iodine, but I had read that vegans often have low levels of it.