Four days ago, I noticed a brown spot on the lower leaf of my FLF. It has grown and has some white residue on the edges, and a second leaf is also affected, and it looks like a third is about to start to brown. There is a little white residue on the top surface of a couple leaves. I thought it might have root rot, so I pulled it out but the soil was dry (I could only feel a little moisture from the outside of the root ball at the bottom.) any ideas on what’s ailing it?

I have had my plant for about 8-10 weeks. It was last watered about 2.5 weeks ago. I typically water it 24 ounces every two weeks. It is potted with miracle gro moisture control soil in a container that has drainage holes. It typically gets light from about 9am-1 or 2pm, but mostly on the upper leaves. It also lost two leaves in December.

Thanks in advance!