I'll guess you're using Solr 7.x and those fields in your schema were
As of Solr 7.0, the schemaless mode field guessing added a copyField rule
for any field that's guessed to be text to copy the first 256 characters to
a multivalued string field. The way it works is a field is created with the
type "text_general", and a copyField is then automatically created with the
dynamic field rule "*_str" to create the multivalued string field.