I just have the eye.
There rarely is just one thing but more several in combination as any one surely can be off. This is nature not a machine....
For yours although large appearing which is usually male IMO it is the 'roundness' of the fins ,both anal and dorsal with particular attention to the anal fin.If it goes past the base of the tail then male...Yours just meets the base of tale at best?
To cap my guess and it is just a guess to which I have been wrong before I see I think a good amount of blue specks in the black spot??? some or just a few around the outside of the black spot I have seen in males ,but when there is that much it is usually a female...
Your link did not work but I think I have learned all the tells already....