Since then, I have learnt to rotate my fertilisers and use those with less nitrogen.
Guanito is an organic fertiliser (probably made with bat shit) that has proportions 6 nitrogen: 15 phosphorus: 3 potassium. According to its manufacturer (see HERE), it also has calcium and magnesium. This is nutritious plant food. Its high levels of phosphorus encourages strong root growth. When growing plants from seed, this is important. A strong root system means that the plant can absorb nutrients well later in its life. Magnesium is important in the production of chlorophyll that the plant needs to convert sunlight into energy it can use.
Calcium is important to build strong cell walls that are hard for plant pests to penetrate with their suckers. Plant pests like aphids and mealybugs suck plant sap. If their mouth parts find it hard to penetrate the leaves, they leave your edibles alone.
Phenix is an organic fertiliser that has proportions 6 nitrogen: 8 phosphorus: 15 potassium. According to its manufacturer (see HERE), it also has magnesium. This is also a nutritious plant food. Its high levels of potassium improves plant metabolism and thus encourages flowering and fruiting.
Plants need sulphur too. So, I sprinkle sulphur flakes to the soil. Sulphur is an important nutrient that affects many different metabolic processes and contributes to production of chlorophyll. If you want sweet tomatoes and bell peppers, you need sulphur because only when chlorophyll is present, can the plant convert the sun's energy into sugars.
Epsom Salts = magnesium sulphate. I dissolve this into water and spray the plants daily when they are fruiting. This ensures that fruits are well-formed and sweet.
When plants are well fed with nutrients, they grow strong and then they will be naturally pest resistant.