The acid damage from the caustic spit begins to show on Aasgar.

Gharmez assists Cici in doing triage on the party, and this is the wounded:
Aasgar ~ 95%.
Abenor ~85%.
Kurst ~80%.

Cici uses her healing hex on all three. Aasgar is now fully healed, and Abenor and Kurst have nothing a good night's sleep can't cure.

The captain orders everyone back to stations for maneuvering watch and in short order the keelboat is moored. Once moored, Captain Bloodtusk says, "Well done on killing those dragons, but the alpha got away with a horse. While you were busy, I had a smoke filter I put on the lens of my spyglass and clearly saw a cave where the alpha took the horse. It's actually not very far from here. I'm asking if you'll go and retrieve the horse. Maybe the dragon already killed it for a meal, maybe not. But losing a horse makes travel a lot harder once we begin heading up the other river."

Cici didn't know what type of dragons they were, but she describes what she does know ... as someone who has some basic understanding of dragon physiology .... to Galakhar. Galakhar tells you all he knows about the creatures from his observation and party reports.
Spoiler: River Drakes
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Yes, they are blue-ish, but they are not the true dragon known as a "blue dragon." These assailants were a lesser known category of dragons known as a "drake," and in this particular case they were "river drakes."

First, yes, they do belong to the dragon family. This means that pound-for-pound, they are extraordinarily skillful, tough, resilient, and immune to magical sleep and paralysis.

Most drakes are able to call upon a burst of speed when moving, which is how the alpha managed to get away so quickly. If Gharmez hadn't been able to shoot that last one out of the sky, it would likely have zipped out of there too quickly to follow.

A river drake is an all-terrain dragon in many ways, though its aquatic adaptations means it is a bit slower than a man on land. They are average fliers, moving at a decent clip but not as fast as a raptor like an eagle or even a crow. More like twice the speed of a man on open terrain. They can move as quickly in the water as a normal human on land.

River drakes can spit a caustic mucus in a very limited splatter area. The mucus is really an enzyme that while corroding everything is designed to help break down flesh. It is a very high viscosity that hardens quickly on contact with air, and if a person isn't careful not only take the initial shock of acid, but they get rooted to the spot while even hardened the mucus begins to digest them slowly. A river drake tends to recharge this mucus more slowly than a true dragon might with their breath weapon.

Given their caustic mucus, river drakes have a high tolerance for other solvents, corrosives, acids, bases, enzymes, etc.

Unlike the nigh impenetrable larger true dragons, the scales of a river drake protect them little better than the thick hide of any other animal.

Does the party gather to go retrieve the horse? The captain can't really make such a request into an order.