Problem with browning Conifers is it weed killer
 

Hi,

i have 5 5ft conifers that are only a few years old and suddenly from one side and from the bottom upwards they are going brown.

i am not sure whta this may be and how to correct it?

However I did kill some weeds that were nearby with weedkiller - could this have got into the the ground and is slowly killing all the trees?

Will the result be completely brown conifers

Any remedies? Should I chop the brown branches off and will new ones grow back?

Thanks