I'm guessing here but...

the darker color is probably closer to the true color since you've removed it from commercial low-light, high fertilizer premises into a private container garden.

Lower, yellowing leaf-drop has many reasons. Could be spider mites which leave dry, rusty-colored leaves with some webbing activity. These little stinkers can defoliate a mini in quick time. Best control during heat is spraying the undersides of the leaves with a water wand set to 'jet' 3 times a week during the summer. Spraying a miticide when it's over 80-90F can cause more damage to both you and the bush.

Oft-times a containered rose will have multiple plants so it's a 'bush' when you buy it. These root zones compete for water, soil and nutrients and will battle to the finish. Even a larger container will only delay the inevitable. The first sign of struggle are the older, bottom leaves. Would be too easy if the canes started wrapping around and choking each other... you'll have to dig the plant back out to see if this is the problem.

When was a the last time you fed it and what did you use? If you have this plant in full summer sunlight and your prolonged heat index is 90F or above, you need to use far less fertilizer and more water until the weather cools down.

Roses have to have good drainage. Does this container have enough unclogged holes in order to let the water run out? If you have a saucer underneath the container, are you dumping out the excess water? It's best not to have a saucer underneath at all but they can also improve the humidity level in dry, arid climates like mine.

How often are you watering? If you're watering an already wet plant, the leaves are going to turn yellow and the canes will die. Allow the soil to dry out a little before you water again.

What type soil did you plant the rose in? Standard ol' potting soil is usually every thing but 'dirt' and roses like a little clay in there. I use a mix of potting soil, compost and garden dirt or a rose planting mix in my containers. Local rosarians also tout using cactus potting mix instead of the garden dirt portion as it's still heavier than the other two.

Did you add any amendments to the soil when you transplanted the rose? Some triple super phosphate or bone meal, along with a little slow-release rose food really helps strengthen the plant as it matures. The phosphate has to be in the soil in the rootzone in order to be available to the bush as phosphorus doesn't move through the soil with water. A little chelated iron is also a necessity. I use it three times a year.

A containered rose goes through nutrients much faster than an inground plant so it needs less product, more often.

Thanks for the response!

Your explanation for the color change is probably right. At least, it makes sense to me.

To answer your questions:

I don't think it is spider mites. There is no webbing, and when I shake the leaves onto paper, no mites fall off - just that coarse granular stuff. I think it would be defoliating worse than it is, and I haven't lost all that many leaves yet, but I am concerned that I might.

This rose does have 4 plants together in the same pot. I potted it up into a larger pot in hopes that I could delay breaking them up until they are dormant. But maybe this is the problem?

The last time I fed was yesterday, and the time before that was last Wednesday. I feed once a week with a balanced 10-10-10 liquid fertilizer diluted to half strength. I water when I notice the top of the soil is getting dry, which is about every 3-4 days in heat. It is not in full sun. It receives full Morning sun, then dappled shade (almost full sun) from about 11 until 2pm, then full shade.

The holes in the container are unclogged, and it seems to drain fine. I removed the saucer because we were having quite a bit of rain for a while there, and while the rose got little of the rain water, I wanted to ensure the drainage was good enough, because the soil was staying wet for a much longer time than normal. I didn't want to have to fight off powdery mildew, as I am having to do w/one of my crepe myrtles.

The soil is a mixture of composted manure, regular organic compost, potting soil, garden soil, and sand. I did not amend the soil with anything else at planting time. I had no bonemeal, and didn't think to pick any up at the time.

Once again, thanks for the advice, and let me know what you think.

--Joe in TX

That's quite a mix you used there. The composted manure along with compost along with weekly feedings may be overdoing the nitrogen but I still think the rootzones are in competition. The sand you added to the container probably wasn't necessary since you also used potting soil and the container drains properly. In our clay soil, I don't use sand in containers but do use some in the bottom of planting holes if I had a tough time digging to begin with and the hole isn't draining to my satifaction.

The course granular description isn't ringing any bells with me. Last time I used that phrasing was right after we had the new shingles put on followed by wind & rain. You already know what aphid honeydew looks like and probably whitefly damage. I wouldn't describe either one as 'granular' but they do leave residue (poop, I guess).

When in doubt, throw a little Epsom salt (magnesium sulfate) on it. I use that here in late August to help with the heat stress. Again, use chelated iron if the rose food you've been using doesn't contain any. I like Kerex Sequestrine 138.

I'm not big on using chemical disease and pest control but I keep some Orthenex on hand when one or the other is getting too hard to control organically. Take the proper usage precautions, of course, if you decide to go that route. I mentioned somewhere else that minis I've purchased at grocery stores or garden centers always seem to have what I refer to as 'kennel disease'... dunno what it is but they get sprayed with Orthenex then stay in quarantine for another 10 days. By then they show signs of new growth and a will to live.

Well, I definately appreciate the help. I'm not sure whether the granular stuff is insect waste or not. I wonder - could it be residue left from water evaporation? Our water is very hard, and I do sometimes get some on the leaves.

At any rate, I will take your advice and separate them as soon as this flush of blooms is finished. An I will also add bonemeal to the soil.

Thanks so much for your help! You seem very knowledgeable!

--Joe in TX