From what I can see In your diary it's mostly lower and middle leaves that are yellowing. Your plant knows these aren't doing much for her anymore and are sucking them dry of nutrients in an attempt to kill them off so that it can send energy to other parts instead. Hope this helps! Happy growing!
lower foliage getting next to no light would not be concerned at all.. If it's it's higher I might be... I don't know in my opinion it's almost a good sign to see that yellowing as she is cleaning up some of the Nitrogen from the foliage and you don't really want excess nitro. If she is growing healthy and the top foliage looks good. You are A ok.