@SLuGGeRNauT_420 You could have had the fungus in the veg stage and now you are seeing it during the flowering stage, because that is when your plants are focusing their energy on reproduction and are thus at their most vulnerable. If you're 100% sure its not that then it could be phosphorus excess. It affects the plant by causing a massive nutrient lockout of other elements like calcium, copper, iron, magnesium and zinc, being zinc the first micro-element to get blocked. In this way, you must check for deficiencies of other elements to correctly diagnose a phosphorus excess and to know how severe it actually is.
If you detect an excess of this element you should flush the roots with at least three times of water than the capacity of the pot. There are products to break down salts to ease the flushing of the roots, which should be always used with an adjusted pH level depending on the life stage of the plant.