yellow leaves and spreding need help..!

my plants are now 18 days old and 3-4in high and there turning yellow

it started with the very first leaves that showed after germation then has started to move up set by set

there about 20 leaves inall on each one of my 4 plants... and 3 outa 4 have all the same signs
starting with the first leaves turning yellow then working its way up

also 3 outa 4 have roots showing out of the bottom of the pots and they are the ones that have yellow leaves
the one with out roots shoing is fine and is a nice green

i feed them 1mil split 4 ways in one liter of water makeing that 1/4mil per plant a week orso a go

i flushed all 3 with 1 1/2 liters of water 3-4 days ago yet the yellow is still showing and starting againg on more leaves

what is going on??? it cant be nute burn or else the 4th plant would be the same
the one that showed roots first out the bottom and has the most roots showing 2-3in is the worst

i have just been feeding them with water since i seen the yellow leaves but its still carrying on

imtrying to get some more pots and soil for them but i have to order it in is it coz they need more room or what?


HELLLLLP..!

dude! all you need to do is change to bigger Pots!! go to the store as soon as possible and transfer thos girls immidiately. roots coming out of the bottom is a huge sign that you need bigger pots! fill the new bigger pots with soil. press the bottom of the current plant container into the soil of yer bigger pot......then loosen the soil on your current pot by squeezing the sides and tapping all around + bottom. then put a finger on each side of the base of the stem. and flip the plant and container upside down.....then put plant into bigger pot. hope this helps.. i didnt know if you knew how to transplant. also after your transplant, water the soil...and pack it down just a tad.

just so you know, as plants get bigger, they need to have more roots. so by putting it into a bigger pot...the roots stretch and grow....then your plant can get bigger.