What size is your tank? How long has it been set up? What are your tank parameters? Salinity, Alk, Ca, Mag, ammonia, nitrite, nitrate and phosphate levels? I only see saw power head it the upper right. Is that correct?
The most common reason anemones split in our tanks is stress. ALK levels changing especially going high is probably the biggest reason. When conditions are poor they split to increase the odds one will survive. New tanks and environments are another big stresser for BTAs. They often split shortly after being moved to a new tank.
It is hard to say without more info. It does not look like there is enough flow or light from the photos. Anemones like to have there foot where they can retract themselves to get away from light, flow and preditors or anoying fish. They also like to be able to extend out to absorbe the light and grab food in the current around them. They prefer lots of light and flow easily accessible to them. It also looks like a new tank. Anemones often strugle in newer tanks until the tanks become more established. Usually around 6 months. Anemones love a tank with nitrates as they absorb it directly as food.
6 T5 bulbs should be plenty light if your tank is 4 foot, but all your photos look very dark.
