plant deficiencies unkown

So I have 6 northern lights special plants from seed. I only have one completely healthy plant the other 5 are showing some weird necrotic spots on like one or two bottem leaves for all of them. It's not heat stress I have them under a 1000 Wt mh at about 24-26 inches away. Growing in ffof soil. No nutrients or fertilizer added ever. Ph is good so I dont know what the problem could be. Also there about 5 weeks into veg. Any help would be appreciated. Also it won't let me upload pic so yea