Answer: I am not really clear on the symptoms you are seeing but here are some thoughts for you to consider. The problem could be related to soil moisture levels. Overwatering causes soggy soil and excludes oxygen from the roots. Roots start to die and rot and the leaves start to turn yellow and die. Drought or fertilizer burn can also damage roots resulting in leaf yellowing, dropping and sometimes brown areas especially around the tips and edges.
A bacterial or fungal rot may also be attacking your plants. These are usually induced by either over-watering or by watering too frequently which keeps the soil surface and the plant leaves constantly wet.
Try backing off on the watering schedule. Apply an inch or so when you water (a coffee can or other straight sided container makes a good sprinkler gauge) to thoroughly wet the soil. Then allow it to dry out before watering again. This should be about once a week or so in the summer.
If the symptoms continue, you may want to take a sample of the problem to your local Cooperative Extension office for positive identification and control measures.
Good luck with your acuba!
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