Complex sentence: Jalapeños are subject to root rot and foliar blight, both often caused by "Phytophthora capsici"; over-watering worsens the condition as the fungus grows best in warm wet environments, however the cause is not itself over-watering but the fungus.
Split into simpler sentences: Jalapeños are subject to root rot and foliar blight, both often caused by "Phytophthora capsici"; over-watering worsens the condition as the fungus grows best in warm wet environments. However, the cause is not itself over-watering but the fungus.