Here's another thought. Plankton blooms are not static. They change. Even if you were able to get a bloom now, it wouldn't be what you want.
If you fertilize now and don't get a bloom, most nutrients will leech out and settle into soils, or be flushed away with rain.
I wouldn't fertilize in the winter. Even if it does no harm, there is no gain. Waste of money.

Teach a man to grow fish...
He can teach to catch fish...