Originally Posted by NANAMAN

My first suspicion would be the water. Chemically treated water wreaks havoc on bio. life in soil, also causing the pH to alter, sometimes radically. IMHO this is a hugely overlooked cause of many growth problems. Last on the list of possible problems would be a virus. I would try to use collected rain water, natural spring water, or the r/o on new, un-established plants. That would also rule out any salinity issues ( dissolved salts).