Hi, 

It does look like some type of fungal infection, probably different for each of them. Our plant pathologist recommends pruning out all the dead growth that you see and trying to examine the stems. If you thin out slightly too it can help bring more air in and hopefully clear up any of the disease. Don't compost or water. You can even take a leaf blower and try to blow out the old fallen leaves that may be harboring any of the disease as well. Also, when you re-mulch, clear out the existing mulch and dispose and apply a light coating of new mulch.

Hopefully the healthy parts of the plants will rebound.

If it is a soil born fungal infection, there isn't much you can do. Soil born fungus is naturally occurring and not something that is treatable. It causes root rot and overall decline of the plant. It usually happens when the soil is too wet so you could check to see if the ground is unusually wet or staying that way for an extended period of time. 

It could also be Volutella on the Pachysandra. When you prune out the infected plants, look for any spots, particularly on the Pachysandra stems, that are black and then prune below that. If there are any legions left, the fungus will continue to spread. It can be somewhat tedious if you have a large patch that you are trying to save. You can also see an article that is published for landscape professionals, an IPM report from a few years ago (page 9), for more information on management, however some of the recommended chemicals used can only be used by certified professionals. 

Hopefully these steps help solve the issues. It may take a little time to see results or re growth through the season. Any new growth that comes up, closely examine for more legions to see if the disease is still present. 

Let us know if we can help further with this or answer other questions. 

Emily