Why did my pills change?

In Binding of Issac Wraith of the Lamb I picked up a Range Down Pill that I already identified. Some time during the play-through it changed to a Range Up Upgrade. I am not sure when it happened or what happened. I know that that the Lucky Foot Item and the PHD can change negative pill effects, but neither one of those items were picked up in this run.

Are there any other items that could of changed the pill type?

If you hold on to a known negative pill long enough does it change?

from the wiki:

Upon entering the Cathedral, all bad pills will become good ones. For instance if you beat Mom's Heart while holding a Tears Down pill and then go to the Cathedral, it will become a Tears Up.

From The Cathedral

So if you were holding the pill as you entered the Cathedral it would have changed.