Neon Tetra dieoff
Over the last few days I had a massive dieoff of my neon school, went from 18 to 3. Ph is 7.2, ammonia, nitrites and nitrates are zero, temp is 78. My black tetras, tiger barbs, and harlequin rasps are doing fine. It's a heavily planted 20g long, fully cycled for almost a year. I'm open to any advice.