Overnight Dorsal Fin Collapse And Discoloration On Pearl Gourami - Please Help!
So this is my first incident on my first fish in my first tank. My tank is heavily planted and was recently cycled and I've had ammonia: 0 ppm, nitrites: 0 ppm and nitrates: 5-10 ppm for over a week. I added 2 pearl gouramis (1 male and the other seems to be a female but I'm unsure) and 3 otocinclus as my first fish and they've been doing great. I feed them JBL Novo Bea, Hikari Tropical Micro Pellets and Hikari Mini Algae Wafers for the otos.
I woke up this morning with a strange sight. His entire dorsal fin seems to be chopped off or collapsed. I know this happened overnight because I was contrasting the two pearls' dorsal fins yesterday when trying to sex them and they were both fine. Throughout the day today, his coloring on his throat/chin has been fading considerably and he is now completely void of color on his throat.
I searched online and the main culprit seems to be fin rot, which can be due to water parameters and ammonia poisoning. I immediately tested my water fearing an ammonia spike but all the results seem perfect. 0 ammonia, 0 nitrite, 5 nitrates and 7.2 pH as always.
I've attached a picture of my tank aquascape and the current condition of my male pearl gourami. This is quite literally my second month in the hobby and I didnt expect my apparently "hardy" pearl gourami to experience this.
Can anyone please tell me what is going on here? and what action I need to take? A part of me is really hoping that he simply cut it on a piece of driftwood while swimming around the tank.