Thanks.
I followed your suggestion and contacted Five Star Chemical's Support.
In case anyone was wondering or finds it useful, I thought I'd share their response:
The actual approved dilution is between 1oz/5gal up to 1oz in 3 gal. 1oz in 2 gal is outside this range. Seeing that the...
I recently got distracted when cleaning my bottles before bottling and mindlessly rinsed my bottles in a no-rinse sanitizer solution that was not mixed to the recommended dilution (should have been 1oz Star San per 5 gallons water). I mistakenly only added 2 gallons of water to 1oz Star San...