Chocolate Haze Indoors - First Grow

Welcome to my first grow journal! I’m super pumped. Initially I tried to grow a strawberry cough seed by Dutch passion, but never saw a taproot. Tried a few different measures to get her going, but nothing worked. Tossing her in a peat pot just in case. As for the star of the show, Chocolate Haze germinated almost overnight, taproot was nice and ripe within 2 days. I planted her in a jiffy pellet (which was soaked in water, squeezed out a bit, and then refilled with some diluted coffee). Another 2 days and she broke through the surface of the soil. The shell of the seed had kept the cotyledons closed until she was about 2 inches tall, so I carefully removed it. Another day and the cotyledons has unfolded to reveal two nice little true leaves, as well as a super strange brown growth on the tip of one of the cotyledons.... does anyone have any clue what this could be? I tried to VERY CAREFULLY poke it off, but couldn’t. Is this a problem that I need to remove? I scoured the Internet for answers and didn’t find anything. She seems to be growing just fine though? And she loved that coffee - I read that coffee has a good amount of nitrogen, potassium, magnesium, and is safe to use as a pH reducer (which was necessary thanks to the alkalinity of the jiffy pot) - and it seems like it was really effective! I plan on giving her more when I transplant. Last question, I’m currently using an old 70W LED that I had bought years ago for indoor gardening, but hoping to upgrade lights after I get a payout from a job I recently did. Anyone have any recommendations for ~$100?