Hello!

Cabbage leaves can turn brown due to several factors. Knowing what our weather conditions are now leds me to believe the following 2 your main culprit.

Calcium Deficiency: Inadequate calcium uptake can lead to internal browning, especially in rapidly growing tissues. Often caused by inconsistent watering or lack of water.

Environmental Stress: Fluctuating moisture, high humidity, and high soil salinity can hinder nutrient absorption and cause browning.

To improve and avoid repeating these problems
keep moisture even, improve airflow, and remove badly spent outer leaves if they are trapping rot or pests around the head.

Below is a site that will give you more details and offer suggestions in case the above is not correct.

If you have any others questions please let us know and do send a picture.

Good luck and thank you for contacting EMG!



https://gardenish.co/learn/why-cabbage-leaves-turn-brown/