You define have mites. The first picture you posted Is absolutely a spider mite. Diluted peroxide is pretty safe . Maybe neem oil ?
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Have you checked for caterpillars. I lost one of my ladies, she was 1.5m tall and started to look real sick. I separated her as I had no idea what was up. The leaves started to droop, turn yellow and fall off. Parts started to turn black as well so I took a heap of cuttings, all bar 1 died and she’s a monster 
. That’s the one on here with the oddball leaves 
. Works out that the plant that died is one that’s infested with mites.