When side effects occur with supplements, the only way you can get an answer, is to stop them. Wait for 2 weeks and introduce one at a time slowly (weekly or every 2 weeks).

I have never had any side effects from benfotiamine. But lipoic acid does have a side effect profile, and may cause these as the dose increases. So I would expect this to be your culprit.

Kiwi is correct...there is a transporter for lipoic acid and this transporter is also used for B5 (pantothenic acid) iodide, biotin.
Our bodies make lipoic acid and it is found in small amounts in some foods. So if this transporter is filled, with high doses, I'd expect the other nutrients to be blocked or poorly transported until that situation changes.

You can Google "lipoic acid transporter" and read the more recent information about this. My internet is stuck for many requests this morning due to weather, I suppose. So I am not linking these myself for now. The transporter is called the MVT
(multivitamin transporter).