I would recommend cutting the flower spike as soon as the flowers are done. Also; you might want to repot your phalaenopsis as your roots look bad. There are articles that will help you through repotting. The plant itself looks very healthy and once repotted it should take off and grow nicely for you. The spike will naturally turn brown when it is done flowering, this is a natural process. Welcome to the site...look around on the boards and you will find a wealth of information to help you keep your orchid healthy.