Burn and decoloration problems, please help!

[logurita]

Interesting. I'm using sunlight, but here, sun is very powerful, i'm in Canary Islands. Maybe that burns are caused by sun.

About plasticbags, there are not soil container, container is two 8 liter water bottles joined, plastic bag are just blocking sun light, but there are not touching pot. I could see soil is very loose, i could see many gaps.

 

[logurita]

Now there is no new burns. Maybe was solved when adding potassium or calcium. I think it was a potassium deficiency from early grow.