Hens and Chicks get their name from how they grow and spread. The mother plants have lateral roots that produce offset chicks that spread and form clusters. In a temperate climate, these plentiful offsets have a moderately quick growth rate. In fact, the plant grows so densely that the outer leaves crowd out the lowest leaves and they eventually die. It's difficult to even see those brown leaves so I would just leave them be. The average Hens and Chicks plant will grow to 4-6" tall and spread to 18-24" wide.