Check your overwintered container plants. Some might not have made it through the winter. Lift them carefully out of the pot and check the root system. A healthy plant will have a firm root ball. Check for vine weevil grubs. These can do a lot of damage to container plants during the winter by eating the roots. Badly infested plants can get killed by them.
How To Deal With A Vine Weevil Infestation
Badly infested plants seem loose and are rocking in the soil when you move them. Most of them can be saved though!
Shake out the roots...or what's left of them. Make sure that you don't miss any of the grubs and replant with new potting soil. Make sure to kill all the grubs! Our chickens love them....
If you have many pots and you suspect vine weevils you can use nematodes that will kill the grubs. A lot of plants can get infested with them but there are some that seem to be at the top of their favorite food list. This includes primroses, primulas, strawberries, saxifragas, sedums and other succulents. Check these plants carefully for the grubs.
The nematodes have to be ordered online. Because these little creatures are alive they have to be stored in the fridge and used within a certain time. Follow the instructions on the packaging. This organic method deals with this problem very efficiently.