How long have you had them? I have a couple of bleached out white palys I got from someone and it's been only about a month and a half and they're coloring up slowly. It takes time for bleached out corals to get their color back.
Some palys/zoas grow longer tentacles due to high flow (that's what I noticed for a couple of my zoas). Some zoas/paly do fine with fish waste as food. When they close up, it could be a defensive reaction instead of them grabbing on food and eating it. There's a debate in the zoa/paly community whether or not if they require spot feeding or just letting them eat fish waste...
As for them turning brown, it depends. Brown could be their original color (you might have "Cinnamon Palys", but hard to say atm) or they turn brown because they're exposed to too much light and they try to counteract it by turning brown. My zoas turned brown but I moved them down the tank and they colored up back to normal.
Either way, what you have, they look pretty darn cool already. Reminds me of white lilys