Answer: I would suspect that the one dropping flowers and leaves is signalling root distress. Plants in containers dry out quickly and sometimes air pockets develop around the roots. Even though you think you are watering thoroughly, water can just be streaming out of the drainage holes without actually saturating the soil. I'd start by immersing the pot in a larger container of water and letting it sit for about 15 minutes. This will saturate the soil completely and drive out any air pockets. Then, since roots in nursery pots can over heat when set in full sunshine, try shading the pot with rocks or decorative pots clustered all around. If you can keep the soil from drying out too much and if you can keep the roots from baking, your bougainvillea has a better chance of recovering. I wouldn't repot the bougainvilleas. Wait until you can get them into the ground. I recommend this because bougainvillea dislike having their roots disturbed and transplanting usually sets them back for several weeks. They should be fine in their nursery containers until this winter when you plan to plant them.
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