Spontaneous yellowing of phalaenopsis leaves.

[R1CHARD4]

Hello! I have an issue regarding the yellowing of the leaves with my phalaenopsis. It spontaneously apppeared within a 2 day timeframe during my absence from home. It may seem apparent as stem rot as a result of improper watering practices; but I beg to differ. I am extremely particular about my watering and take extra measures to prevent rottting whenever possible. The yellowing appearing to spur from the stem (I suspect a fungal infection). The plant has a had a history of spider mites and issues where some roots were drying out not due to desiccation nor rot. These issues were all addressed but I thought I would be helpful to specify the history of the plant. I would love some help with this case. I have attached images as a reference. Thanks!