Hello, we live near Austin, TX and three weeks ago planted three pinapple guava plants, each 24-30" tall. I added a little organic fertilizer to the top soil when I planted them, and a small amount of root stimulator. I watered them daily for the first week or so, and then every 3-4 days since then. They are in an area between some oak trees where they get 4-5 hours of sun per day.

For the last few days some of the leaves on two of the plants have turned from a deep green color to a lighter yellow green. Some of the leaves that changed color also have brown spots on them.

Is this from over-watering, or something else?

Thanks in advance for the help!