I had planted few stone apple plants (perennial, flowering and mid summer fruiting trees) in plants. Due to insect larvae most of leaves were eaten. So I put in handsome amounts of Urea, Diammonium phosphate, and Potassium Chloride in the pots in the topmost layer in dry form in order to save the remaining plants (I didn't use insecticides as I didn't want to contaminate the plant). To my amazement the plants which had few leaves remaining started to show leaf burns and plants dried up. Question is what causes burns due to access urea, though urea is required by 'all' plants, and is there a way to cure such burns if detected early? I had earlier put good amounts of urea in seasonal crop/grain plants, but most of them flourished. What could be the reason?
Chloride is generally a no no. How big are the pots? I'd dig out the top inch or so and rinse, rinse, rinse. Lots of liters/gallons. Unless you are sure what you are doing, stick with readymade fertilizer mixes like 10-10-10 NPK. Sounds like you over salted your plants, which sucks the water out of them. Look at one and two. Rinse the soil enough, and your plants may come back.
-Originally intended as a comment, but it's too answery for that.