I doubt the anemone starved to death-what type did you try?Many will do fine without ever being fed-I only feed my bubble tip anemones when I want to force a split.Your tank is still new,in terms of reef tanks & your nitrates are a little on the high side.I'd give the tank more time to settle in,before attempting another anemone.,as they like excellent water quality,flow & lighting.As for keeping them with leathers,I've never had any problems-unless they are in direct contact,in which case one will sting the other.HTH