the plant has defencies, potassium is most evident, the brown necrotic areas look like burn

I agree the soil is poor, most of these low end bag soils that are barky seem to have an excess of ferts pre-added to compensate for the low quality or lack of soils and maybe burning the plant or Have you recently fertilized this plant?

additionally , although difficult to see in the photos , the new growth seems to be twisted & distorted, I would do a soil runoff test to rule out PH issues


complete a soil runoff PH test.......
with PH corrected water (6.5-6.8PH for soil ) pour enough water in the pots so the water runs out the bottom of the pot ...collect & test the PH of this runoff water....post both the watering going in the pots and the runoff ph