I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
I guess if you got some of the weed and feed on them that could be a problem. However by your description I suspect that soil moisture extremes may be the cause. Both dry soil and soggy wet soil can kill roots and cause symptoms of top death. Damage in transplanting or putting dry fertilizer in the planting hole can also result in root death and top dieback.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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