Did you transplant it recently? If you did, it might be going through shock. It probably is also running out of energy for new healthier grow. I went through similar problem with my other berry. I kept them in the platic container from Wal-mart, they had been growing slow and the new leaves were not vibrant. I recently put them in ground, and mix the soil with some "Peat Moss", the new leaves are now looks better, I guess they get more new energy/nutrient now. Raspberry needs acidic soil, get some Peat Moss into your planting area, and get some soil acidifier powder from your local nursery, mix it with water then spray the plant and ground around the plant. It should improve within 2 weeks.

cjsm, thank you so much for the follow-up. I am hearing rather conflicting messages from different people though - my local nursery people told me to keep on watering, since this is a new tree and the root system is not well-developed yet. On the other hand, I hear what you are saying and the overwatering theory in clay soil (which I also have) definitely makes sense! I think I am going to stop watering it for a few days and see what happens. You know, it's hard when you see the leaves drooping in the strong afternoon sun and still not water it! At least it is getting cooler around here these days... BTW, cjsm, my tree was planted in a big planting hole on a slope, and I had plenty of cow manure and things amending the local clay soil, so I think I don't need to take it out to raise it more. I hope this does the trick! Thank you again for your info.

If you are sure that your clematis is getting enough water, then this sounds like a classic case of magnesium deficiency. Some tomato fertilizers contain magnesium since tomatoes also need this trace element. If you cannot find a tomato fertilizer containing magnesium, which in general can also be an excellent choice for fertilizing clematis, an epsom salt solution is an alternative magnesium supplement. While it is impossible to make a general 'prescription' that will fit all cases because it is impossible to diagnose the exact deficiency without a full soil test, you can try the following recommendation. Mix one teaspoon of epsom salt to one gallon of water. The mix can be applied in quart amounts at the base of the plant over a period of time until the yellow goes away. You should see fast results. Keep any left over solution for future applications, if necessary. Above all, use your own judgement on how the plant responds.

I live in a studio with only a north-facing, floor-to-ceiling, wall-to-wall window. The rubber plant is right by the window. While there is rarely any direct sunlight, it is fairly bright during the day. I water the plant only when the soil gets pretty dry.