Answer: Soil pH can affect the nutrients available to plants but it won't necessarily change the flower color. Irises prefer a slightly acidic soil (6.8) but are tolerant of soils in the average range. A very alkaline soil can be improved with the addition of peat moss and/or feeding with an acidified fertilizer.
Now come the questions - did you add your Ebb Tide irises to a bed with other irises? If so, it's possible that the other irises sprouted but the Ebb Tide did not. If you planted them in a bed of their own, it's possible that they were mis-marked and you actually purchased a light lavender. Lots of gardeners think that their irises change color over the years but that's not possible with hybrids. However, the lavender colored irises are the hardiest of all and they will grow long after the hybrids have died out. In 3-5 years an iris bed full of color can be overtaken by the lavender species irises which have multiplied where the hybrids have died out.
Hope this information sheds some light on your iris problems!
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