Strange spots on leaves, anyone seen this ?

[darkb16a1]

Hi everyone, I'm new to Chilliforum and quite new to hydroponic growing as well, and need an advice on what may cause the problem that can be seen on a picture below.

I am growing in both EBB and Coconut Coir, PH 6,2-6,5 , EC 1,2 with NPK 24-23-29 hydroponic fertilizer. Plants looked fine but when I left for vacation and asked my sister to take care of chillies, while promising that she checked the solution's PH and EC, these spots started to appear on both plants grown in EBB and in Coconut mixed with Perlite.

Anyone seen this ? What could it be ?

http://img263.imageshack.us/i/fleky3s.jpg/