Ok, this has nothing to do with nitrogen toxicity since you're not giving her much to begin with! This has everything to do with how much water you're giving her and I think you're overwatering although you don't give any info on how much that is in a 24-hour period (if you give her 1 gallon of water every three days, for example, then you're giving her .3 gallons in a 24-hour period)... So take care of this issue... lift the pot up if you think she needs something to see how heavy it is - or stick your finger in the soil down about an inch or two... wait to give her something until the pot is SUPER lightweight or the top couple of inches is dry. Overwatering is the quickest way to kill your plant...
Good luck!
