It's outside. Something came along. Took a bite and moved on or got eaten by something bigger. Inspect the underside but odds are you'll find nothing. Nature for the most part is self correcting. The only things I spray for outside is Powdery Mildew and Caterpillars. Green Cure and BT. BNW
Spinosad like that is the big gun I pull out when I have a real infestation like white fly or spider mites. It's bigger gun then needed for Caterpillars. Like using a sledgehammer to hunt mosquitos. BT is only effective against caterpillars and is a biological organic rated product. Local garden shop should have it. Bacillus Thuringiensis I like to only use the minimum strength products needed to get the job done and avoid using large scale theater wide chemicals. BNW
I would buy Cal Mag. Back down your solution a little and compensate with some Cal Mag. Don't over do it.