Posted: 07/04/2015 at 09:54
Sorry, didn't answer all of your question.I think the bottom plant is a differnet variety of dracaena or it could be a cordeline - difficult to see.
Overwatering could be the problem for the yellowing. Most plants die from overwatering more than anything else. Let them dry out between watering. Also it looks like they are potted into lovely pots but there are no drainage holes in them - this makes it dificult to judge watering. If I wee you I would repot into plastic pots and then place them in your lovely pots. This way you can water easier, see when plants are root bound and need to be moved to a bigger pot. Hope this helps.