Dr.AddMedPHL said:

If two explanations both fit, the useful question is which one predicts something the other does not.

Coming at Dr.AddMedPHL’s question from a different direction. Take it one variable at a time. Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent argument can untangle them after the fact.

Happy to go further on any of that.

Adding the numbers, since they settle part of this. Practical: whatever you change, write down the date and the reason. In three months the reason is what you will have forgotten, and the reason is what makes the record worth having.

Correct me if the detail matters more than I have assumed.

Following on from Dr.AddMedPHL — and this may be the naive question:

What did you change at the same time, and can you separate the two now?

kate.chem said:

Practical: whatever you change, write down the date and the reason.

I read this differently from kate.chem, on substance rather than tone. This treats a plausible mechanism as a demonstrated one. Plausible is where you start looking, not where you stop.

kate.chem said:

Practical: whatever you change, write down the date and the reason.

That holds where the measurement is reliable. Where it is noisy — and a lot of what gets tracked here is noisy — the same reasoning produces confident nonsense.