I'm not sure how universal common names are in Corydoras, and I figured you would do better looking for images for comparison with your fishes using the scientific names. A quick check online gave the following common names for the two: C. melanistius - bluespotted corydoras, blacksail corydoras, blackspotted corydoras, dotted corydoras, Guiana cat or Guiana corydoras; C. reticulatus - reticulated corydoras, mosaic corydoras, network catfish, or network corydoras.
Tony