I'm looking for the name of a series of books (and/or their author), written in English. The storyline followed the last surviving members of a race(?) of people with magic powers corresponding to the classical four elements, residing in an otherwise typical fantasy world. I think there was some kind of church organization that condemned these people to death if found.
The first book followed a young woman with "water" powers, which translated primarily into being able to heal people. The memorable feature is that for the main character, employing her healing power required her to square off on some kind of spiritual plane with a sea serpent-like monster representing death. The first book opens with her living a solitary existence on the edge of the sea and occasionally healing people. The second book involved the heroine of the first book finding and taking charge of a young girl with fire powers. The second book at least left open the possibility of a third book, but I never read it, and don't recall noticing if it had been published.
Other random clues: I read the first two volumes some time around 2008, although if I had to guess they were probably written in the 90s. Fairly sure the author was female, and likely near the beginning or end of the alphabet (I got the books from the library; I have a visual memory of picking them up from one end of the sci-fi/fantasy shelves, which would have the beginning of the alphabet on one side and the end on the other). I think cover of the first book featured a woman fighting a sea serpent.
EDIT: Some further details I can recall (partly because they differ from the first answer I got): The first book definitely featured only a water person. Besides the fire girl mentioned above, an earth person appears around the end of book 2. Fairly sure all the magic people were female, though whether that was part of the worldbuilding or just coincidence, I don't know. I do remember that whatever wiped out the magic people happened a while in the past of the story, and the land was currently at peace. The first book had some kind of typical romantic subplot between the water heroine and the local prince/duke/male-royalty-person. This would seem to rule out the Elemental Logic series pointed out in one answer, which based on descriptions appears to feature a variety of LGBT relationships (which is cool, but doesn't match my recollection of this particular series).