It's a Latouria type dendro. I haven't even had it a month

It is in its bloom cycle.
I have been watering 2x week, always until water runs out (distilled water only). To be honest, I'm not in a big hurry to look at roots because that always ends with me repotting which then seems to make things worse. The best repotting experiences I've had have been using lava rock. So maybe I'll peek on the weekend, when I have more time and I can get some potting stuff together.
So physan isn't meant to apply to plants? I did look at the St. Augustine reference and the Physan is more affordable than Banrot. I wasn't expecting to see dark spots from insufficient watering, so this is a new one on me! I thought for sure this would be some kind of infection.
My other dendros (same type) are doing fine which also threw me off. I got a Little Atro months ago, and I have to say, I don't know what to look for at the roots. For this L.A., the roots are always a pale color, there are no aerial roots (weren't at time of purchase). I kind of have to soak it because it is so tippy, but the roots don't change color or seem to be rotting. Or doing much of anything. Honestly, they kind of look like straw which doesn't seem right, but the plant seems healthy enough. With catts, phals and anything with new root growth, it's much easier for me to say healthy, or boo.
For the oncidiums, I think I'll just leave them alone, I don't want to make things worse. I'll take pictures later when the light is better.
Thanks for the help! I never would have put this together with needing more water. Getting the water right is where it all falls apart.