Sprouted seed few days old has burnt tip need help with reviving it

Hi I have a baby raspberry cough that sprouted is about an inch tall, has not yet started to produce flowers, I'm currently using coco coir soil and a LED veg light. I have used nothing but distilled water, the seed itself is in a larger blue solo cup and I have a small clear solo cup at an angle over it with a few holes in it for air, and to keep the humidity. I noticed yesterday the tip was starting to get burnt, so I put it in the dark for a few hours. because its been on a 24 hour light schedule since it sproute only made it worse. I have not yet used any kind of root extender on it like I did with my other plants. was not sure it needed any nutrients at such a young age. what are my best options to keep the plant alive? should I cut the dead tip? or use the rooting extender? which is a 7-1-1 nutes. I need to figure out something or get some kind of advice very soon before I loose the plant itself for it is a feminized seed, and a strain I have wanted to have for a while. (supposably very good for pain) since I shattered my femur and wrist in the last year, and had multiple plates and bolts added to my body.