Answer: It is possible to over-water and over-fertilize barberries, but it's also possible that since you've only recently planted your shrubs, they're responding to the change in sun exposure and perhaps wind in their new locations. As long as your soil drains well, the roots should be happy with one-inch of water per week during the growing season. Build a watering basin beneath each shrub by mounding up a few inches of soil; fill the basin and allow the water to drain, then fill it a second time. Watering in this way concentrates the moisture over the root mass and allows it to trickle down and wet the entire root mass. Wait 3-4 days after watering and dig a hole down near the roots of your plant; if the soil is still moist 3" beneath the surface, you won't need to water for a few more days; if the soil is dry, you'll need to water; if the soil is soggy wet, it's remaining too moist and your barberries will begin to show signs of stress.
Best wishes with your shrubs!
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