I have this Madagascar Pin Palm or Pachypondium Lamerei which has been attacked by some kind of fungal or bacterial infestation.
I've been using an antifungal solution, yesterday was the 3rd application (spraying the solution mixed with water once a week) but it doesn't seem to get any better as new black spots appear on the back of new leaves (see pictures).
I have been using Amystar from Syngenta mixed in a water solution according to instructions from the producer.
Does anyone know what this is and if there is a better solution?
It doesn't have any pests, at least none that I can see and it didn't have a pest infestation before.
I water it every almost 5-7 days and it sits in full sun for about 5-7 hours in a South-West window. The soil is specifically for cactuses/succulents and the pot has a drainage system in which the extra water can spill.