Last night, my BTA fell off the rock it was perched on - It now looks in really bad shape - Could it be possible that a crab/shrimp has started eating it? The clowns are still tending to it - So, is it dead?
Alas, I think it's a goner. It has the classic symptoms of an anemone wasting away. I'd remove it from the water ASAP. If it stinks to high heavens when you get it out of the water, you know it's already decaying. Prepare your nose for the assault.
Anemones can die for all sorts of reasons, but my first hunch would be a bacterial or protozoan infection. Malnourished anemones don't die in this manner.
Temperature has been oscillating between 78.5 and 79.8 (climbing when lights are on, then decreasing) - I had added the BTA on 12/27 - It was looking great until a few days ago when it went in hiding, then fell from its rock last night...
Did it ever attach? Could be an infection like Len says, even a secondary infection due to injury, but hard to say. Some just don’t make it, but if your water parameters are in line I wouldn’t let this discourage you from trying another – preferably a captive clone. They are hardier and the impact on the environment is nill.
I had a similar situation with one of my BTAs a few months ago. I cut off the necrotic tissue from the part that looked to be still alive and it healed and has regrown. It took some time to get back to the original size, but BTAs are highly regenerative. Mine started when a rock fell and scratched it and then it started to get that infection. If you try this, definitely keep a close eye on it and siphon it out if it starts to fall apart.