Anyway, looking at your set up and livestock below:
40G tank. No chiller (temp avg 28-30). 30 white LED, 30 blue LED, no T5. No skimmer but WC with NSW 20% every 2wks once. Turbo snail just KIA. Remaining 3 Damsels, 1 tang, 1 maroon clown, 1 cleaner shrimp.
I would say you are asking for trouble by running your system without a chiller and also without a skimmer. If your anamone died and rotted away in your tank, I'm very sure your nitrate level is already sky high.
WC with NSW 20% every 2 weeks is not considered a lot especially if you are going skimmerless. You should know that your tang is a poop machine. Without a skimmer and keeping a tang, you are really asking for trouble.
As I mentioned in my above post, get a test kit and test your water parameters. If your NO3 is sky high, then do a 20% WC daily until your NO3 reduces to a reasonable level.