hey Zaffieken, the burnt tips are from overfeeding and it got worse for two reasons : first it takes time for a plant to recover, it's not that easy. Second when you water with plain water it makes the nutrients in the soil more available . What you need to do instead is flush. Flush is : water until runoff, then water 20% more, then squeeze out the excess water from the bag. in this way you get rid of the extra nutrients. I garantee if you do this you will see the plant recover.