Queen has nearly stopped laying mid-dearth — normal August brood break or is she failing?

Vermont, second year, three hives. Inspected yesterday and my strongest hive shocked me: barely any eggs, a few patches of young larvae, mostly capped brood and emptiness where the June brood nest used to be. Queen is present — I saw her, she looks fine, still has her mark. We're in a hard dearth (goldenrod hasn't started). The other two hives have also slowed but not this dramatically. My anxiety says failing queen and I should order a replacement before sellers run out. My reading says colonies throttle brood when nothing's coming in and she'll fire back up on the fall flow. How do I tell the difference? Is there a test short of waiting and maybe losing the window to requeen?