The Same Deadly Vitamin Deficiency Is Ravaging All Kinds of Animals

Is not a bad hypothesis but is not the only one.

Those symptoms are familiar to any fish pathologist. There is a common freshwater fish disease that typically causes whirling behavior and massive mortality in trout and salmo larvae. Exactly the same behavior as claimed. Thus Nature peer reviewers may want to consider my alternative explanation: What if Thiamine was irrelevant here?

If you put fish larvae in a concentrate of X, you are directly modifying (increasing) the osmotic pressure. Thus parasites are killed (by osmotic shock causing cell bursting). Decreasing the parasite load to acceptable levels means that fingerlings now have a choice to build a inmmune response, deal with the disease and recove. Thiamine could be directly related with developping inmunity, of course but an alternative possibility is that this is an artifact and the real effect was caused by increasing the osmotic pressure.

Your move.