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!
Very strange about those gardenias. However plants can be that way sometimes where some live and others decline while getting the same treatment. Something is different in the soil or some other factor. Perhaps a root rot? Your County Extension Office may be able to look at some photos or a sample and better diagnose the cause.
Just take care to keep the soil moist but not soggy. Time will tell whether the ones going down hill will recover or not. There is not much else in your power and fertilizing won't help with this.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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