First off...the stupid questions are the ones that we don't ask...
So you do not have to apologize. In the article it stated a systemic chemical, with this you apply and it goes into the rooting system to the plant in general instead of soaking the leaves to penetrate into the plant. Which would answer the condition of the plant before pitting (inside/out).
I would definitely get the water tested. It appears to be a process of elimination. I would first start off with testing the water. I know when I do not have rain water to water mine with, I put tap water in a 5 gallon bucket, cleaning it with alcohol first, and fill the bucket up and let it set for no less then 24 hours to 2 days. This should help with releasing
chemicals.
I wish I could help with a name of a systemic and if I remember correctly and hopefully she will chime in is Gin, she has spoken in the past about a systemic chemical she uses for her chids. Sorry for the senior moment
Wish I could be of more help.