A couple of things could be at play here: Raised bed soil tends to heat up sooner than ground soil. Radishes are a cool season—and soil—crop, and you may have gotten them in after the soil warmed. Soil is often the culprit when vegetables/edibles fail to thrive. Radishes prefer sandy loam with a pH ot 6.6–7.0; below 6.5 lime should be added. Too-low pH (for turnips) can also result in clubroot, a fungus that causes cruciferous crops (of which turnip is one) to fail to form. Warm soil, high soil moisture, and acidity (low pH) favor the presence of the fungus. Spores can live in the soil for up to 20 years—but can also become inactive/nonviable after a 2-year respite from the host crop. This points to the importance of rotating crops, or, at least not planting the same thing in the same place year after year.
A couple of things could be at play here: Raised bed soil tends to heat up sooner than ground soil. Radishes are a cool season—and soil—crop, and you may have gotten them in after the soil warmed. Soil is often the culprit when vegetables/edibles fail to thrive. Radishes prefer sandy loam with a pH ot 6.6–7.0; below 6.5 lime should be added. Too-low pH (for turnips) can also result in clubroot, a fungus that causes cruciferous crops (of which turnip is one) to fail to form. Warm soil, high soil moisture, and acidity (low pH) favor the presence of the fungus. Spores can live in the soil for up to 20 years—but can also become inactive/nonviable after a 2-year respite from the host crop. This points to the importance of rotating crops, or, at least not planting the same thing in the same place year after year.
We hope this helps!