Since it seems Stinky helped you out, I'll just give you these for future reference:
Revised: The Complete Guide To Sick Plants,pH and Pest Troubles - PlanetGanja.com

and

Steve's place - Plant Mineral Nutrition

I definitely dig the second page. It explains things easily and clearly. For the first plant: You're not using a pre-nuted soil are ya? Also, it looks decently deep in that Solo cup, maybe a half inch/inch down? If so, repot and raise her, or add a fan; maybe she's not getting enough airflow. The second, chill out on the water and skip the fert for now. She's growing a root system right now and living off the cotyledons. Don't fertilize until at least the cotyedons die off.
CultureCherryPopper Reviewed by CultureCherryPopper on . Someone please confirm my hypothesis: My plants started off green and vibrant. Then: -I noticed grey tips on the bottom leaves which turned yellow plus twisty bottom leaves -After the yellow they (the tips) turned brown -After the brown tips the whole leaf started yellowing -So I flushed and left it for a day -The day after I flushed again with pH'd water (1gallon; container is 14oz.)and immediately nuted with pH'd nutes (you know, like i add the nutes then ph the water) with recommended dosage for seedlings -Now the Rating: 5