DenPhal indentations on leaves

[KristenReuel]

I bought this NOID den/phal for next to nothing during the winter. It looked almost dead, but soon put out a new growth that grew so fast I thought it would reach the moon.

However, it has recently stopped growing, and there are indented spots on the leaves. At first I thought it might be sunburn, but the bottoms of the leaves are much worse than the tops. I haven't seen any pests on my orchids, except for one that had those miniscule little bugs that eat decaying matter.

The denphal has TONS of roots with growing tips. I repotted it once I received it into woodchips/coconut husk. I think I should have washed the coco husk more, but the roots are growing like crazy and when I water it the water now runs clear.

The indentations appear to be radiating around the base of the leaves, near the stem. I'm also certain that no water would have gotten in there. What could it be?