Is sodium bi-phosphate same as phosphorus?

Ive been cheap and was using sodium bi-phosphate from a aquarium ph set to drop my ph. The last few days my plants have started to look unhealthy and are now showing signs of a major zinc deficiency. I read that excess levels of phosphorus can cause a zinc deficiency, so im wondering is sodium bi-phosphate similar to phosphorus??
ive got some proper ph down now from the hydro shop and flushed so hopefully it clears up. any thoughts?