Whats wrong with my Cordyline?

Hi Roger you've answered your own question I think being in a pot it needs more watering/feeding than the ones in the ground.

And The Bottom leave's on Cordy's naturally turn brown and die off, pull them off and u will see the trunk, its turning into a tree Roger :)

It is natural for the lower leaves to die back as it grows on, this is your plant turning into a tree forming a bark trunk. DO NOT tear the brown leaves off this may cause damage to the trunk. CUT them off as close to the trunk as possible.

Your Plant looks like its suffering from starvation, water and feed, give a high nitrogen foliage feed also.

I have been growing Cordyline from seed for years. If you grow them in a pot container it will restrict growth considerably. However, if you keep them well watered and fed they should be okay. As well as giving them a feed of dried blood, fish and bone meal give them a foliage feeding too. There are a number of factors that you should be aware of, which ones are you going to be growing ie; red and purple, green or varigated. I ask this as one is less hardy than the other, the purples are more prone to suffer from root-rot if planted in a waterlogged situation, more so in winter when it can cause root rot, the greens are more hardy. What I do in winter with the smaller ones is gather the leaves together and tie them up, covering them over with hessian to protect the crown from the frost and freezing winds.