I would advise against the nutes (sorry pollack), simply because your roots can easily be burnt. Honestly it looks like your soil is too moist, and its not getting enough air. an 80/20 mix seems VERY lite, the only reason you add perlite into the coco coir is JUST to bring air in, the more perlite, the more air.

I've got a bean I popped 4 days ago, almost the size of your little sprouts now I think your over watering, OH and make sure you have drain holes in your solo cups, you don't want that nasty water sitting there - I typically have to hit my solo cups every 3-4 days with about 1/3 cup of water each (when I do soil grows)
low_rdr Reviewed by low_rdr on . My turn - Stunted growth? Using coco, but this form seems more appropriate than the hydro form. What is your experience level? (first timer, novice, experienced...) Noob (first grow) Your Equipment: .1) Type and wattage of lights. (MH, HPS, CFL's, tube fluorescents, LED's) T5 Florescent 4-2ft tubes in fixture .2) Distance from tops? 4-6 inch .3) Reflector type? (cool tube set-up, bat wing, enclosed reflector, bare bulb...) built-in (fixture) .4) Is there a consistent fresh air supply? Maybe not -- it's in Rating: 5