What does it mean if I have yellow leaves?

Usually yellow leaves are caused by over-watering.
 Sometimes we kill them with kindness.
 AVs do not like wet feet.

 I water my plants from the bottom using a saucer that I fill halfway.  come back after one hour, and if there is any water left in the saucer, I dump it out. That way the plant only takes what it needs.

They should dry out a little between waterings. You can tell by lifting a plant and feeling it's weight whether it needs watering. Of course, you can also stick your finger into the soil.