My clownfish has been acting fine in the past 1 month I've had them, no signs of trouble, and actually the only fish in the tank that haven't been stressed by anything.
Yesterday I introduced a featherduster, Galaxea coral (Tooth coral), Xenia coral, and 2 yellow sea cucumbers to the tank, the Xenia coral coming with 2 emerald crabs, a fancy yellow brittle star, and a peanut worm.
Today, both of the clownfish are suddenly seeming very stressed, one won't stop racing around the tank, bumping into anything he swims towards before changing direction, the other is slowly swimming near the top, bumping into snails and walls. Both fish have some kind of white coloration to their faces, looking like they just got hit in the face with flour, and I snapped a picture and noticed their gills are extended
I tested the water quality last night, pH is about 8.0, alkalinity 300, nitrites 0, nitrates 5-10 (The strip was a creamy color), specific gravity 1.025 (33ppt)
Whitish coloration to face, and extended gills (black "fingers" behind first stripe) best seen in 2nd pic
1st pic is the larger female swimming near the top, 2nd pic is the smaller male racing around
I'm not sure if this has anything to do with it, but I also noticed some spiderweb-like strands floating around in my tank.