It sounds like your issue is the green you're seeing, vs feeding; although you will want to feed larger particle food. My concern would be placement. It sounds like you're getting some algae growth which is a common problem with sea fans. They need to be kept in very low light and high flow; primarily to keep algae from growing on them. If it is algae, try moving it to lower light or putting more flow on it
Very hard corals to keep. I'm building a 400+ gallon sump, auto feeder and mysid propagation system, primarily to attempt long term success with them. They are incredibly beautiful corals (not worms) but right now, 12 months is considered long term!