Fungus Gnats in Royal Gold Basement Mix??

I was using Fox Farm Ocean Forest on my first grow, and decided to try Royal Gold Basement Mix on my second grow and compare results.

Well... ever since I brought the Royal Gold home and started using it a couple of weeks ago or so, I've noticed I had a few fungus gnats invade my garden. Luckily I've been able to get rid of them, i think. But what the hell? Has anyone else picked up this mix and had the same problem? Or could it be the FF originally, and they just didn't show up til later??

Thanks for the input,

i picked up white fly after buying a plant at a nursery thanks.....can a bag of soil say 20# be sterilized if so how?