I have never seen scaly leg mites in a pullet in her first year of laying, and agree with @rebrascora that these may not be young birds.
Castor oil, crisco shortening, petroleum jelly, and coconut oil are all good thick oils that can be applied once a week and rubbed up under the raised scales to smother the mites and help new scales grow in. Before that I would do an initial warm soak indoors of either soapy water with Dawn or Epsom salts water and very gently brush the scales with an old toothbrush to lossen scales, then dry well.