Yellow spots

[Kollba]

Hi.

First some background...
I live in the tropics so I keep my orchids outdoors in a "house" made from iron pipes and shade net (shadow net? English is not my native language...). I had to replant ALL of my orchids because I am new to orchids (6 months) and didn't know how the rainy season would affect them (and this year it was more rain and more rainy days than normal) so I got a lot of mold and rotten roots. I kept my orchids in wooden baskets but had put far too much chopped coconut in them and packed it too hard. Now I have learned that lesson...
I took out all orchids cleaned the baskets with 99% isopropanol, used hydrogen peroxide to disinfect the roots, put a thin layer of chopped coconut at the bottom of the baskets, put the orchids back and hoped for the best. I did that about one moth ago.
Many of them got yellow leaves that fell of after a while, but they are growing new roots and it looks like almost all will survive.
Also... I took out all my vandas and attched them to a piece of wood instead of returning them into baskets.
The net is said to filter out 70% of the sun but I think the truth is closer to 50%. I water them once a day with water from my own well (twice if it is hot and windy, but strong wind is rare here). I spray water on the whole plant - not only the basket and/or roots because the leaves dry very fast in this climate (except for the rainy season). I fertilize them once a week by spraying some local orchid fertilizer in the same way that I water them.
The temperature varies between 25 to 40 (max at daytime) and 12 to 25 (min at night). The highest and lowest temperatures are normally just 1-2 weeks in a year.
That was the background and now the questions:

Lately I have got some yellow spots on some (too many) of my orchids and I need help to find out the reason so I can take appropriate action.
The spots are the same on the underside of the leaves. On the orchid in pic 1, two leaves started with yellow spots and after a few weeks both leaves turned completely yellow and died.
The orchid on pic 2 has the same kind of spots but even the leaves without spots are more yellow than they normally should be.
What can the reason be?


I read somewhere that the purple color on pic 3 is caused by too much sunlight. I have about 10 orchids (not only vanda) that has purple leaves to some degree but most orchids has not. But in a way it is logical because during the rainy season it was often cloudy and now it is sunshine most of the time.


And finally the brown spots in pic 4. I think it is some kind of lice, but I do not know the english name (shield lice in swedish - yes I am a swede). If I scratch them with my finger nail they fall of and there is a yellow spot where they were stuck to the leaf. I guess poison is the only way to get rid of them, becuase it is not possible to pick them one by one down between the bulbs. I have some strong shit they use for killing termites, but I am not sure if it will also kill the plant...
On the other hand... As long as there are only a few on a leaf they don't seem to cause much damage and I guess I can never get rid of them completely.

First time adding pics so I am not sure what will happen...