Shiny rasbora?

[Tacocat]

I have a pair(2 of same species, both female[I think]) of Boraras Malactus(pretty sure they are), in my 5 gal. Lately I noticed that in the mornings one of them becomes shiny.


You can see it's eyes, gills and tail are shiny, while in these cases the other rasbora's gills are the only parts that are shiny.


Does anybody know what this is?

EDIT: all water parameters normal and in safe levels.
I love duckweed(kind of but not really)

 

[Tacocat]

Also the cardinal tetra that photobombed is missing an eye, just in case anyone was wondering why it looked weird

 

[Colin_T]

probably a male showing off/ displaying