Vanda Black Spots

My Vanda Sanderiana is 7 yrs old ( 4 yrs in my care) I noticed that the side facing the sun on my bathroom window has this black spots and the four bottom leaves have turned yellow. The side facing in, is clean, green and healthy. I feed it according to instructions and spray it with insecticides, even if I know that it will not get in contact with bugs or virus from other plants(this is the only plant in my bathroom since it is very large plant...I did research but found nothing...please help me identify this spots(if it is not a sickness then I will just let it be) I scraped it off with a butter knife and rub alcohol on the spots

Same is happening with my Rhynchostylis Gigantea(picture #3), I isolated it in another room with same window sun and scraped it with a butter knife and rubbed alcohol on it and sprinkled cinnamon powder on all infected area.

[Greybeard]

I'm not sure what is causing your black spots, the yellow leaves is probably natural the older bottom leaves do turn yellow and drop off, I don,t think you need to worry about that. If your spraying for bugs and you don't have a bug problem maybe that is causing spotting You might try looking into some of the threads that address fungal problems, I haven't had a spot problem as yet I can't post pics. either

gee, Thanks Greybeard...maybe I am just paranoid...maybe I have had these for quite sometime but its just now that I am learning stuff that I am nitpicking...I hope there is nothing wrong

[Greybeard]

Don't feel bad I'm new,I have one Phal. noID and two new little guys from the grow projcet #3 and thats all I do is keep asking myself if I did something wrong. Thats why were here and all the other Geeks As I said I'm not familiar with fungal problems so you can never ask too many questions or do too much research to be sure Just give the others time if they don'y respond right away they'll be on to help

[digitalgate]

the black spot can caused by secondary fungus infection, while nothing serious it is a permanent mark. You primary problem can be mite infection(or any small biting insect). So alternate weekly neem oil with other pesticides should keep the pest to a minimum. you can keep the fungus in check using carptan, thiram ..

Thank You ! digitalgate, I will follow your instructions