Clary sage isn't that strong. I use herbs all the time. I would be more concerned about sunscreen lotion, face wash residue on your hands, or hair spray. If you think the water is contaminated, just change out the water.
I keep my QT bettas in the bathroom opposite to my sink. There's been plenty of times where I wondered if got a little hair spray mixed in with their water. I use lids now.
Also I've kept a couple by my kitchen sink, but then I stopped once I was using my 2% bleach sanitizing spray, I could see particles of the spray rising through the sunlight. Nothing happened.
I've used the bay leaves you typically cook with to soak my injured bettas in. I've also used maple leaves, oak leaves, mulberry leaves, etc.... Nothing happened.
About the pellet shooting behavior, it's nothing to be too concerned with. The red boys I got from IndianaB were doing the same thing with the other pellets I was trying to give them. Finally after 5-7 days all of them with the exception of the little female are eating all the different foods.
The only time the bettas get flakes is if they're hanging out in the guppy tank. It's a little bonus to them in addition to the other fish, it's funny to watch the bettas with flakes because they're not sure which one to go for since they're scattered all over the top. Anything that remains the betta can't eat, the guppies will clean up.
In your other thread, your female betta looks like it's gotten too much food. On the positive side, at least it's eating the prepared food, instead of the other fish. I put blue Delfine with the guppies & the radiation green/yellow colored guppy nipped her fins and she TORE him up. Normally when I see a fish on it's side, it's dead within hour. I removed neon guppy and placed him in a kosher salt solution and he righted himself in about 3-5 hours, but had no interest in food till around midnight. Now at least he's eating, but he's being kept to himself in the floating breeding cage till his fins grow back.
What I've learned is.... Senetti & Delfine are NOT guppy friendly.
But the neon green guppy, he was always the biggest troublemaker & really the one that nipped at any of the bettas fins, so he had it coming. Mr guppy was pressed up against the bottom of the plastic breeding cage taking his final breaths. He's lucky I got home in time to save him. I doubt he'll make a speedy recovery in a week like most of the bettas do.