Dianthus Turning Brown: End of Bloom or Problem?

Dianthus around mailbox, 6 weeks in, suddenly browning. Two scenarios:

Flowers only brown: Normal end of 6–8 week bloom. Cut stems to foliage; enjoy foliage rest of summer.
Whole plant brown: Drought, fertilizer burn, or fungus. Fix: never fertilize dry plants, water deeply less often, avoid frequent foliar wetting.

Diagnose by pattern. Flowers-only = natural cycle. Whole plant = cultural issue.

Annuals: Reviving a Mature Umbrella Plant: Diagnosing Wavy Leaves and Bark Changes; Universal Brown Spot Diagnosis: Fungal Management for Any Plant; Why Are My Houseplants Turning Brown? A Troubleshooting Checklist; Calandiva Brown Spots and Stem Scars: Oedema and Natural Leaf Scars; Oyster Plant (Rhoeo) Brown Tips and Limp Leaves Indoors; Brown Patches on Winter Avocado: Wait for Spring Sun; Cymbidium Leaf Tip Browning: Salt Buildup or Infection?; Seed Pods on African Violets: What They Are and What to Do; Brown Spots on Nepenthes 'Miranda' Leaves: Sunburn or Leaf Miners?; Dealing with Worms in Bird of Paradise Potting Soil

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