I was thinking the same thing. Overwatering can cause the roots to die and the plant starves. A felt pot sitting on soil may not have been allowing the bottom to dry out so the bottom soil remained wet. I think anaerobic bacteria grow in wet soil(thus rosters question about smell).
@Slab has these grates in his posts that might help get the pot up off the soil. The reason the plants on the deck in pans are not showing a similar symptom could be due to the deck heating up a bit and drying the soil more than the plant in the ground. Wet soil and the bacteria that likes that can make the soil acidic also which would lock out nutrient uptake. I am just spitballing here and it may be too far gone which is sad. You take such good care of your plants and have your growing ‘going on’ well. The degradation of the plant do quickly surprises me. I feel badly for you.
