I was thinking the same thing. Looks like birds nest which loves to go up in smoke first and is hard to stop RTN on it once it starts. I think I've lost 4, all at different stages of growthThat’s way too big of a regular salinity swing when combined with Alk and ca tweaking. I’ll bet my left arm it’s not a parasite. I have had the same problem many times and it’s always a water quality issue.