Which anemone did you get? ritteri anemones are difficult at best. They need very intense lighting and lots of movement. They move a lot when things aren't to their liking so you have to watch them like a hawk to avoid disaster around wave pumps. The one in my journal was moved to a 4x2 and has since split 3 times. No rhyme or reason to it either, it gets to about 40cm and splits off. I keep mine under 250w metal halides, 6500k Iwasaki bulbs which are getting harder and harder to source. I have been trying them under different LEDs with little success. They seem to need more in the red, orange, yellow end of the spectrum instead of the blue, green end.
They take up to a week to totally settle in and open up completely. The green based ones I just got from Australia took 8 days to fully open and look nice. The ones out of Africa and Indonesia open up within 3-4 days and look great
If they're emitting a lot of slime, something's amiss and you're going to need to take action quickly with antibiotics. ritteris can melt in a very few days, 3 to be exact.
You're also going to need to ditch whatever corals you have in there, ritteris will kill them and they can open wounds on the ritteri that will cause its demise. My monster wiped out a plating Montipora, Galaxea and Turbinaria.