Toxic levels of phosphorus in the garden prevent plants from absorbing and using other needed micronutrients, even when those nutrients are present in the soil in sufficient amounts. The most common micronutrients affected for plant use are zinc and iron.
Symptoms of plants with phosphorous toxicity present as deficiencies in iron and zinc in the younger foliage. Iron deficiencies cause a yellowing of the leaf while maintaining green veins. Zinc deficiencies present as a bleached appearance to the younger foliage.
The only way to know for sure if the levels of phosphorus in a garden are too high is to have the soil analyzed. If the results reveal that there is indeed too much phosphorus, the only remedy is to cease all fertilizer applications that contain phosphorus and wait for the levels to drop back to normal over time.