How much of what kind of manure, Jason? As the soil warms, too much or too fresh manure will start to damage roots, especially on conifers, most of which aren't too happy about high levels of nitrates.
The distribution of manure is also important: Big lumps or layers of manure underground are going to cause trouble, too, even if well rotted.
Well-aged compost tea might help, as long as not too much green matter (or more manure) went into its composition.

Check the base of the trunks, see if there are any signs of softness, rotting, cracking or splitting, please.