cough syrup taste?

TCA taint or cork taint is best described as a wet cardboard sort of smell, so the cough medicine taste wouldn't have been caused by that.

Considering the time of year and the length of storage it's unlikely that anything you've done has messed with the wine.

There's a few possibilities. One is that our perception of wine chanes with the circumstances we're drinking it. If you're having dinner with Scarlet Johannsen the wine will always taste better than if you're drinking alone at home.

Another possibility is bottle variation, where the different barrels blended together are not blended evenly across the whole batch, creating good and bad bottles of wine that is supposed to be identical. Spanish wines are usually the worst offender in this category.

Finally the wine could have been lightly cooked, i.e. exposed to higher than desirable temperatures for an extended period. From what you've described this is the most likely culprit.

Cough mixture/syrup is often used as a descriptor for wines. Sometimes it's a good thing, sometimes bad. If it is over-powering then I'd suggest that it was a goner and Pauly's suggestion of 'cooked' seems most likely.

Pauly: What did you have with Scarlet?

Yellowtail, and it seemed finer than any Grange I've had