Where is the nutrient burn damage? Your leaf tips aren't even yellow let alone brown? They look pretty healthy to me. If you are worried about hot substrate, then flush it, but i don't see any need for that. You have 1 goofy leaf at the bottom of one plant as far as i could see. Put that in your rear view mirror dude. They look fine so if it were me i would just roll with it till they start to look like they need food, then feed. But for right now they look good and if what your doing the last 8 days is netted that result i say roll with it. Those girls will want around a 800ppm solution when they are fed next time, but they are ok right now in my estimation.