brown spots on leaves

[mamamaria]

my first post, so hi all!

 

i'm doing my first attempt with 3 exterior plants. I planted the seeds already late (7 July, spain) but till now just water them, and gave the nutrients. I changed to the blossoming nutrient 2 weeks ago. I was noticing that the bottom leaves where having a problem, some getting yellow too soon and dying. They start to have this brown spots from the steam to the leave, looks like rust, and then they die. Last week I went to the store where I bought all the stuff but they where closed to holidays, so I'm having a hard time seeing the plants dying slowly

 

I attach a picture os a leave, this one is already on the top of the plant... really don't know if it have any chances to save it...sad... sad...

 

hope someone can help me out, I've no experience at all.

 

 

thanks