During tuning you probably pres one of the reeds to much down or you lift reed to much up. Maby the problem is in the gap between reed and reed plate. Try to adjust problematic reed by little bit and see what happens.
But why tuning that small amount of out of tune. I noticed that is better for notes go little bit higher (like your 443Hz). Because when you blow harder note (tuning) tend to go little bit lower.
P.S. sorry for bad english 🙂