Thanks for the clarification, freyar's wording of the breath weapon streamlines it now.
Since we modeled the extra damage off horrid wilting, I'd suggest a slight revision, lifting text directly from that spell...
Breath Weapon (Su): A tourmaline dragon has one type of breath weapon, a cone of gas that transmutes water to a semi-solid milky substance. Creatures in the area of the breath weapon must make an additional Fortitude save or be slowed for 1 round per age category of the dragon, except the breath weapon does not slow creatures with the Fire or Earth subtypes. This breath weapon is especially devastating to water elementals and plant creatures, which instead take 2d6 points of damage per age category of the dragon.
Very Young: They can manipulate the color of their scales to produce a color spray effect once per day.
Juvenile: Waveform, three times per day (molds a 10-foot cube of water per level into various forms, such as enormous waves; on solidified water this acts as a stoneshape spell).
Adult: Hypnotic pattern twice per day, even while otherwise attacking or spellcasting.
Old: Camouflage ability, 50% invisible, plus 10% per age category beyond old.
Venerable: Illusionist spell effects: change self, mislead, displace (as cloak of displacement), spectral force, halluncinatory terrain, and vacancy; to a total of 20 rounds per day.
Great wyrm: All of the above powers at will.
I find all of those appealing.