Maybe cause of the spotting but pops will have a better idea.Male?
Both are same age. I bought them together 2 months ago. I'm attaching a picture of the bottom one I had taken at the time I bought him.looking at it starting to lean first 2 pics and the last 2 pics the same fish, first 2 I would go female for now. last 2 appear larger and leaning male. again age. size helps.