The term bitten sounds like something is taking a bite out of the leaves. Possible culprits would be grasshoppers, beetles, and caterpillars. These pests usually don't do enough damage to warrant spraying. The fact that leaves are browning suggests either dry soil or soggy wet soil conditions. Both cause loss of roots and result in such symptoms. Try to keep the soil moist but not soggy. It sounds like you may be overwatering the plant and since soils in your area are often black clay and don't drain well the planting hole can become an underground bathtub holding water too long.
Feeding it with light doses of plant food is fine.
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