Strange spot

[fishaholic]

On my pregnant platty, there is a dark orange spot forming on her caudal fin. I have no idea what it could be and am a bit worried.Please help.

 

[black angel]

can you get any water tests done. ph,ammonia, nitrites and nitrates would be good. is there any signs of red streaks on the fins?

 

[Tempestuousfury]

Was it like that since you first had it or did it develop?