I just lost a 2 year old colony to nudi branchs. Could have saved them if I had started with a pest dip instead of a cleaner. If you have zoas randomly close out of no where start a dip off in coral RX or any pesticide dip safe for zoas. If you dont have anything flake off, give a day of rest and the next day after the rest dip it in some kinda cleaner or antibacterial dip. I've brought zoas back from crashing on me with revive before so I recomened that. Usually if it's not pests and some kind of infection from being dragged, stung etc. I'll use revive every other day and place them on a small frag rack elevated in direct flow. That seems to help keep that brown slime/film off them. Peroxide also helps if you dont have anything else. It wont kill alot of pests but may irritate them into letting go while swishing the coral around.