Strawberries in the greenhouse! It’s great! How long have you been cultivating strawberries in the greenhouse? As far as I know, universal fertilizer for strawberry is complex: 10 g of potassium salt + 80 g of ammonium nitrate with superphosphate + 10 liters of water. Use this solution every other week. And I also know that flowering plants need boric solution spraying. You should dissolve 1 g of boric acid in 1 liter of water. Good luck!