Yellow spots on leaves

[Paphio76]

Hi!

Sorry my english.

I am worried about these yellow spots on my Paphiopedilum leaves. They grow very well and are blooming too but there is something wrong because these yellow spots keeps coming.

I water with rain water and fertilize with Akerne Rain mix. Before i use to give full amount but have now give 1/3 ewery Time i water. I also now flush once a month with tap water and that has quite a lot of calcium.

They grow under growlight 10h Day. Use to Be 12, did cut that down to 10.

They had mealy bugs on them sprayed 2 Times with systemic and they were gone. That was 3 months ago.

Are they over/ under watered or fertilized?

They grow on bark/ perlite. They have good roots and growing more of them too.

Few pictures.
Thank You very much If i could have Your opinion.

 

[big923cattleya]

It looks as if something liquid has stained or maybe burned the leaves. Do you get water on the leaves? Try not ot do that if you do. Make sure you water early so that by the time the lights go off, the leaves are dry. See if that helps.

 

[Paphio76]

Thank you for your answer! Might be that too. I water from above but not on leaves. Before i mist "fog" to raise humidity, but have not been done that anymore.
After using systemic i have not "washed" the leaves, maybe could that be problem?

 

[big923cattleya]

Misting is not a good solution for low humidity. Trays filled with gravel under the plants will hold water and raise humidity much more effectively. A humidifier would be even better.
I myself have a house that once the heat is on for winter, my humidity drops to 19% in my house. In my plant room, under lights, I have those trays to catch and hold water. The humidity in that room, under the lights, is often between 52 and 80%, depending upon when I water. Without those trays, misting would raise the humidity only by a few percentage points and only for a few minutes. The little bit of moisture would be negated by the dry air in my home.

 

[Paphio76]

Thank you. My humidity is between 30-40% now on winter when we have heating on.
I do need to put those trays with water to get humidity up.