besides calmag plus is there any cheaper alternative to get calcium back in the soil?

i am completely out of money for the month from buying fungicides/sprays.

one problem though....another plant was put directly into lightwarrior/ocean forest and suffered the worst rust/black spot of them all. i couldnt even get a picture of it because it died so fast. serenade and sulpher had no effect on it whatsoever, whereas the serenade works on the plants in coco.

so im not sure the coco is exactly the problem although im sure it isnt helping much from what you say.


so any ways to get calcium into the soil aside from calmag, and pouring milk on them?