Discolored spots on bottom set of fan leaves

Ok I recently germed some AK-48 and master kush. Finally got my babies under a 400w HPS and things seem to be going pretty good after getting the conditions in my grow area under control. On 2 of the 6 plants the bottom set of fan leaves has some spotting on them can anyone tell me what this is?

im not sure, but it could have something to do with ur nutes/lighting. doesnt seem like a big problem though