Answer: Nasturtiums are generally disease free but do attract sucking insects such as aphids. Aphid feeding can cause a yellowing, stippled look but generally do not cause crispy brown edges on the leaves. I'd look instead to cultural practices. Over-watering can cause this, as can fertilizer burn. You might try immersing the pots in a larger container of water to help leach fertilizer salts from the potting soil and to eliminate any air pockets that may have developed around the roots. Feeding every 2-3 weeks with Miracle-Gro is fine, just be sure to periodically immerse the pots to help rinse out accumulated salts. You can pick off the affected leaves (which will encourage additional growth). Best wishes with your nasturtiums!
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