tom..your trees need time to adjust. Suzanne

Tom,

You don't say where you are living, but I am guessing it is not deep in the citrus-growing regions. Without any more information, what follows is a guess, so please don't act on anything unless it fits the reality.

Suzanne's point is valid, but I would add that you are also stressing the trees by moving them in and out. You don't say if the outside temperatures are in the 50s, or 60s, or 70s, 80s, etc. While the 60s and 70s should be fine, even if they are the case, I might keep all the plants in warm (68 to 85) sunny room (85 degrees in the direct sunshine) for a week or two to let the roots recover from the repotting trauma. You may want to keep the one plant out of the direct sunshine, even indoors, for a few days or a week. In other words, if you put the three healthy trees right up against a sunny south-facing window, put the third a few feet away or behind the others if they can provide some shade.

Also, you say you "teased" their roots out, and that may help avoid circular root growth, but it also adds to the stress. The one unhappy tree, if it is the most actively growing and flowering of the four, is probably having difficulty drawing in enough moisture to keep up with the moisture that is evaporating from the young leaves and flowers. More water is not necessarily the solution: less wind and direct light may well be.

Another solution, if the problem persists, is to snip off the drooping new growth if it does not seem to recover: this will rebalance the plant's roots and branches/leaves.

Even without the drastic course above, if all is still reasonably well with the drooping citrus, you should see an immediate turn for the better if you move the plant into a less extreme environment and I am right about the cause. Usually, within a few hours a drooping new branch will recover. If the plant does not recover, I might suspect the root system was damaged by the teasing process. If that is the case, the need to balance the plant is more pronounced.

If you keep the plants outside, try to find a place sheltered from any strong winds. Once the trees are happy they should be able to take direct sunlight for the entire day, but remember that 1) they will need water very frequently on warm days, and 2) black plastic containers get very warm, and soil in even lighter-colored containers can get quite warm, which is not necessarily good. Up here in Connecticut, my plants spend the summer outside and I end up drip-irrigating them for about 45 minutes a day from 5 to 7 days a week from mid-June through at least mid-August.

Hope this helps,

Don