It will slow and possibly contain the spread in concentrations above 0.3% but it won't cure or heal the existing damage.
Can be a helpful tool, it's not a complete replacement for fungicides. In severe cases, fungicides like chlorothalonil or mancozeb may be necessary to control the spread of Septoria.
Citric acid can be absorbed into the leaf and for the most part is beneficial up to a point. Citric acid is used during cellular respiration to produce energy but it won't do much to stop the septoria and could potentially cause toxicity if over applied.
UV-B at night is more for powdery mildew, it can help prevent septoria likewise but not as effective. UV-B radiation damages the DNA of fungi, disrupting their ability to germinate, infect plants, and reproduce.l UV-B radiation offers a promising, sustainable, and potentially cost-effective way to control powdery mildew and other fungal diseases, but careful consideration of dosage, wavelength, and application methods is crucial for success.
More hassle than it's worth. Being outside doesn't help.
Fire always works Muahahhaahha *evil laugh*