Between 2005 and 2012 there was an anime on Toonami where a man and woman were in space and one of them was covered in green eggs or crystals or something and they were in love. One of them was dying.
This could be Eureka Seven, which aired on Toonami between August 18, 2012 and August 10, 2013.
The two main characters, Eureka and Renton, fall in love. At one point in the anime, Eureka is covered in what looks like a green rash, as shown in this clip:
They don't know at first what is happening to her and they may think she is sick (I don't remember). In actuality, it is not a rash. She is just in the midst of a transformation, part of which involves growing wings (she is not human):
I don't remember if any of the series happens in space. They do have a ship that is capable of going into "low orbit around earth". There were a lot of scenes that took place within the upper atmosphere.