Leaf edge and tip curled down

This plant is suffering from long term over feeding. Giving more feed will not fix anything, only make things worse. Always water with plain water first before fertilizing.........never fertilize a plant in dried substrate. You should also adopt a schedule of plain water/plain water/fertilizer........never fertilize every time you irrigate. I would suggest just giving plain water, no nutrients at all, until the plant stops curling down and growth picks up. Do not fertilize again until the plant is looking better! The brown blotches (burning!) is from nitrogen toxicity......it is NOT a deficiency of iron, magnesium or potassium!! And yes, getting run off each time you irrigate is essential.