Your Shefflera needs Micromax for the Iron. It wont fix the old yellow leaves, but it will fix the new growth. Chop it like its hot.
The T5HO lights are insufficient. In your picture, see how the tops are getting light? Great! That's all. The rest is just in the shade. Sun moves from east to west. Your T5HO light stays in the middle.
Lastly, the picture where you show the light about 2 or 3 feet above the tiny bonsai trees, is waaaaaaaaaaaaaaay too high. You want your trees to be an inch from those lights. If not, it's just making the room bright, the plant doesnt see any of it. This is the conversational way to remind you of the Inverse Square Law of Light, where "Indoor
grow light that is positioned five feet above the
plant canopy is 50% less powerful at that height.
Inverse Square Law basically states that the farther away an indoor
grow light source is, the less effect it has on an object, and this formula is geometrical in its diminishing effect". AKA you arent the Sun, so move those plants to the light source best you can.
Cheers