Just like the title says.

I use both plant foods for good foliage and flowers.
All the other plants sell within 15 min, but the last plant consistantly will never sell, even when leaving the nursery up for hours.
I am just selling plants to make money for upgrades right now, and all the plants I'm selling are Daisy Ferns, so they're all the same plant.

I have the blue soil and water.
The last plant is never infested, or sick, it's perfectly healthy.
I have tried moving the plant to a different stand, and periodically lowering the price.
I have even lowered the price all the way to $1.
If I leave it up at $1, eventually it will sell, but it takes about 15 minutes.

This happens every single time I sell.
What's going on with this?