You sometimes get brown leaf tips on cyms so I wouldn't worry to much.
They are quite happy pot bound, and healthy plants seem to fill pots pretty quickly. They do like well draining medium though so make sure water is draining through well.
I would leave it while it has flowers, but re-pot seeon after to give it the whole growing season over the summer to grow new roots.
When you repot, if the pot is full of roots the advice is to remove the bottom 1/3, this helps encorage new root growth and is another reason to do this in the spring so that new roots grow to replace them.
I would advise getting a good medium from a specialise orchid nursary or supplier.
www.repotme.com is meant to be good.