Answer: Since some are doing fine I would expect your care is good, so based on your description I would suspect there is some difference in the planting/growing conditions that is causing the problem. You may have two different sets of soil conditions. For example maybe one bed was amended at one time with compost while the other was not, or one bed is primarily subsoil due to soil being moved about when your house was built while the other still has the original top soil, or one bed is much drier than the other either due to drainage patterns or a failure of the watering system. There might be a big difference in pH and/or fertility from one bed to the other. There can also be cases of accidental herbicide exposure where a rotary spreader has cast lawn weed and feed on the bed. There is also the possibility that one set of plants was rootbound or otherwise stressed prior to planting and has not rooted into the surrounding soil as a result. You might want to dig one up and see. Unfortunately I can't tell you specifically what is happening but I hope this helps you troubleshoot. Your county extension and/or professionally trained nursery staff may also have some ideas.
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