These yellow ones are just old leaves that will fall off as new leaves come in. Normal.

Oh, awesome! Thanks!

Inside the plant, the leaves get shaded out by the newer leaves above them. Leaves perform several important functions...they shade the plant, protecting it from sun burn and a bit of frost damage; they permit transpiration, the flow of water from the root tips to the ends of the canes; and they photosynthesize food from resources and light. The most important of these is the photosynthesis. If there is no light, that leaf isn't feeding the plant, but it IS sucking food from the plant to support itself. Plants are the perfect "commune". All parts perform their designated functions or the plant sheds them. A leaf gets shaded out and the plant absorbs the sap from it, turning it yellow (red, or other color, depending upon the genetics) and then it falls off. As long as those yellowing leaves are inside the plant where there is little to no light, or down low on the canes with lots of nice, healthy new growth above them, ignore the yellowing as it is totally normal. It's when the newer leaves, out on the surface, the canopy of the plant begin yellowing, you have something to worry about.