im guessing itsa combination between your heat and nutes....try to sty at 30 or under......dont use pre nuted soil....its crap and kills everyones plants ussually....read everything on this forumn and you will do well on yer next grow
hey pop you didnt have to type all that in even though its good to know but i tell you this 1.5 liters is not a big pot and your post seems to be little confusing on whether its hydroponic or soil . but as far as my eyes will let me view your plant looks like you may be having light burn . tell you what move your lights a few more inches away trim your burt leaves and flush well with water and watch and see what happens .ps try bigger pots like 5 gallons if it is a soil grow .
looks like nute burn to me if ur soil has nute already in and ur put nutes in every 2-3 days then ur just building up the amount of nute u have in the soil, but if its just at the top then ur lamp is to close, flush and raise ur lamp, idealy u want to flush with 1 and 1/2 times of clean water(nothing added just plain water) then the amount of soil try that and see what happens good luck
1.5 litre is 1/3 of a canadian gallon and you should be in at least a 2 gallon pot with drain holes. if yer candian like me - look for pro mix HP - its sold all across canada. your 600w HPS should be at least 2' from yer plant tops. are you feeding with the lights on - because that looks like splash back on the leaf; this is when the water/nutrients get splashed onto the plant leaf and then a prism effect under the lights burn yer leaf.