Color me unsurprised. If I were worried about fertilizer going where it should not be, I would take a hard look at formulation, frequency of application and rates of application. I have mentioned that I live with very erratic weather. There is no rainy season here. A cold front can show up any month of the year with no rhyme or reason. Therefore, I do not ever apply a high rate of fertilizer at once with the expectation that it will last for three months. Not even a slow release granule. A flooding rain can cause that stuff to float out of the lawn and into the waterways. So what do I do? Apply liquids at a low rate on a regular basis. If there is a cold front hanging around causing it to rain for a month, I cut back the rates to no more than what the grass can immediately absorb and utilize. During dry periods, the rates can go up, however I manage and control the irrigation. There is no run off and excessive leaching is avoided. That is another thing. Florida is sand, right? There is nothing more asinine than limiting watering to so many days out of the week on sand. On the few lawns that I maintain that are on almost pure sand, irrigation is set to a baseline of 1" of water per week divided into daily waterings. There is no sense in flooding sand and expecting it to hold water for the rest of the week. That flooding also serves to put whatever chemicals are in the lawn straight into the ground water.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738