Answer: Weigela in general tend to leaf out a bit late in the spring, but if they are all planted close together I would expect them all to be showing signs of life at the same time.
Weigela sometimes suffers some winter dieback, and the dead branch tips should be pruned away in the spring. Routine pruning should be done immediately after they bloom since they bloom on growth formed the previous year. You can also give them some compost and/or a complete fertilizer such as a granular 10-10-10 according to the label instructions in early spring and again about two months later. A year-round layer of several inches of organic mulch is also helpful. Since the plants were set out last fall, you will still need to water them to supplement natural rain fall as needed to keep the soil evenly moist but not sopping wet through this fall.
Sometimes, fall planted shrubs can suffer extra winter stress if they are not sufficiently watered during the fall while they are becoming established underground (the soil should be kept evenly moist but not sopping wet until the ground freezes), or if they were very stressed while being held over the summer in the nursery and so were just not very vigorous any more by the time you planted them. Last summer was so dry, and fall was also so dry, that this may be what happened.
You might wait a bit longer to see if they are able to sprout from the roots, but it is also possible that they are simply dead. I'm sorry about your plants.
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