Hello, welcome to JustAnswer! I am a licensed veterinarian, and I'll be happy to help you in any way I can.
I'm sorry to hear that Margot isn't acting normally.
It would be unlikely for these recent changes to be associated with the recent recall - for two reasons.
one, it's an entirely different variety (OM, for weight management),
and two, a lack of Thiamine would usually cause neurological signs, as deficiency affects the brain.
so, I'd be more likely to suspect a metabolic condition such as kidney disease, liver disease, diabetes, or other conditions such as cancer, or heart disease, all of which are very common in elderly cats.
Often, the only signs of such illnesses may be the signs you describe.
Therefore, I'd have to urge you to have Margot examined by a veterinarian, in order to have some blood and urine tests done to make a diagnosis.