I don't know what the back spot is from but I don't think I would worry about it. Overall the plant looks healthy. Do you know which paph. you have there? I love all paphs. and am currently working with micranthum and armeniacum. My first micranthum of the year bloomed a couple of days ago. I have a tray of micranthum and many are in low bud but didn't do so well with the armeniacums. Maybe next year will be the armeniacums year and the micranthums won't bloom.