You should be OK. I doubt that a quarter pack of dry yeast will dramatically change your beer. My guess is that much of the activity you are seeing is the WLP300.
As a rule of thumb, you should have made a starter. I've made a lot of really good beer just pitching the vial, but you do run the risk of underpitching.
Brody's Brew House
Primary: Sweet Potato Saison(
Seconary: Don't use one, generally
Kegged: Scottish Strong Ale
Planned: Either a Porter or an AIPA. Possibly a RIS.
"For a quart of ale is a dish for a king." - Shakespeare