Well the bottom leaf looks like natural leaf drop, old leaves will eventually do this.
The top leaf which you describe as dark blueish back actually looks to me to have a dark red tint over the green. It looks to me like it's reacting to brighter light. I often notice newer leaves do this more than older ones. At this level the light is not too high, but it is just getting more than it used to perhaps.
The spotted leaf would be more of a worry to me. Keep an eye on it and make sure those dark patches don't spread.
The new roots growing look really good, the old roots around the top of the medium look really bad. Have you ever taken it out the pot and looked at the roots inside, how are they, are they good roots or soft/mushy/hollow ones? I think it would be worth checking them.
Your post appears to be in the right section by the way. I didn't think you could move it yourself, though moderators can