It is the begining of heat stress or light stress The distance from light to plant looks good, I am not familiar with celcius so I can't say if it is to warm in there. I did see you recently put them under a HPS and by the looks of your grow you were using somthing with alot less lumins. So that leaves light burn and from what I see it is minimal and not a major concern yet. Put a fan in the room for air circulation and try using a NEW spray bottle ( not one that was used for any cleaner or chemical, residues from the previous chemical could have a devistating effect on your plants )and spray the plants occassionaly with just plain water to suppliment water to the leaves and help keep them cool.
Jerry Garcia 2007 Reviewed by Jerry Garcia 2007 on . weird spots on leaf can anyone tell me why i have these weird spots on the leaf?.. i have just started the flowering stage at 8weeks with the 250w HPS bulb..hanging at about 80cm-1m above plants, and before this post, nutrients were not given to the plants... but when i saw the leaf with those spots i figured that maybe it could be due to lack of nutrients.. so i have just given them a solution which consists of 11.5N, 6.5(P2O5), 10(K2O). 3ml of solution was mixed in 2l of water... Rating: 5