Something in going on in my tank?

[Delphinus]

Symptoms sure sound convincing that it could be a dinoflagellate bloom. Is it really light in texture, like it falls apart easily?

If it is a dinos bloom ... Good luck, you're going to need it. I've lived through it twice, both times were nearly the end of the hobby for me, so be prepared for this mentally. It can be a really tough slog.

Starving them of light seems to be the key to overcoming them, you may need to go as long as a week without any kind of light over your tank. I think Christy even needed to put a towel/curtain around her tank in the end.