It appears that your weeping spruce trees are dying as the result of some event that has occurred in the past year.  The needles which are dying look as if they were healthy last year but now are dehydrated.  Fertilizer will not help this situation.  Some factors that can lead to this type of die-back may be excessively wet soil or excessively dry soil.  It could be related to an herbicide that was applied to the soil or sprayed.  It appears, however, that only the weeping spruce in the pictures were struggling.  You also mentioned that you had lost 5 arborvitae trees.  Arborvitae trees often die in the first couple years after transplanting due to either inadequate or over watering.  They are also sensitive to certain herbicides used on lawns.  I would recommend removing the dying plants as they will not recover and not plant the same species again in the same area.