I need help!!!

Ok hears the deal i been tryin to grow 4 da last 4 mouths and my plants always end up the same dead i know that im new to this and they say start with some easy to grow strains but i had my heart set on growing some purple wreck but the whole thing only lasted 3 weeks im fin to order some more purple wreck im not goin to give up this is my new hobbie this what happen as soon as my seeds germinated i put them in the hydroponic system i know u post to wait 2 weeks for good roots to show but i find this to work quicker they was doin so good after i hit them with sensi grow part a and when is the best time to use fans when big or small because i start usein it at the begaing of the growth but they was moving real slow but when i turn it off and left the light on 24 hour they started gettin bigger leafs were gettin greener the heat from the grow box was doin them real good everything was good i check my the ph twice a day ontill one day left for about 4 hours i came back they was dead do u think some body did something to them cause they was just fine before i left can smomeone tell me wat im doing wrong and wat i need to do here are some pics to show wat happen and wat im usein to grow

dude i feel for u , whats the reccomended dosage on those nutes for seedlings? and how much did u give them ?what is your PH ?how hot does it get in that box ? your fan is fine leave it. and if your saying your plants were great until one day u left and came back 4 hours later to discover your plants fried .....wel it sounds like someone is killing them, unless u added the nutes that day b4 u left then when u came back they were fried=thats to much nutrients frying your plant.

switch to soil and you won't have these problems

Hopefully the "did someone do something" isnt a real question and no one knows that they are growing there.

It seems very odd that the plant could even go from healthy to that in 4 hours O.O

What is your grow medium?
How often are you changing the res?