Thanks, everyone. Overwhelmingly (both here and responses to the same question I posted on the Facebook "RC Turbine Jets" page) the responses have been that I should assume that the fuel has algae, I should clean out my tank/UAT/onboard systems (and fuel jug), use Biobor to deal with any algae and start over with new clean fuel, using Biobor in my fuel jugs going forward. I also have the Mr Funnel filter to remove water and will continue to use that.
It's a small pain to have peace of mind and much less bother than a flameout...