Help with my first vanda - Brown spots, lost roots

[adam123]

Hi everyone,
This is my first post on the forum. I've quite recently developed a fascination for orchids, and over a few months, I have gathered a small collection of about 20 orchids, that I grow in my apartment in southern France. I just can't seem to stop buying more! Most of my plants seem to be thriving, with lots of new growth and flowers. However, my Vanda, I believe, is in need of help! I hope some more experienced growers will be able to help me.
First of all, my Vanda is growing in a large glass vase directly under a North facing Velux window and gets a few hours sunshine per day. I water it daily by dunking it in Brita filtered water with some fertilizer. I only recently moved it to this spot. Before, I didn't feel it was getting enough light which is why I moved it. Ever since I moved it to a sunnier spot, it has developed a large amount of black/brownish spots on its higher leaves, almost over night. Is this just due to its new environment and more full sun, or could it be a more serious problem? The spots are mainly located on the top leaves which receive more sun.
Next, I try to remove dead roots as often as possible. I don't see much point leaving them on, but the result is that the amount of roots has halved since I bought it last year. It has however recently started growing a large amount of roots. I suppose my main question is: Is my plant healthy? Am I doing anything wrong?
When I first bought it, I vaporized the leaves daily, but not systematically with filtered water. I noticed a sort of white residue on the main stem. Is this simply due to limescale? What is the best way to remove this?
Enclosed are a few photos to help understand my query (roots and spots), and a picture of it in flower, just for fun!
I hope you'll be able to help me better understand my Vanda's requirements. Thanks everyone!
Adam