somthin went wrong...again

my first plant that i ever started growin died today "R.I.P" all i can do i tell you what happened and if you can tell me where i went wrong id appreiciate it...
So far this has happened to two of my kids. the plants got to about thier third tier lookin healthy, then they just stopped growin and slowly shrank to nothin, i am using distelled water, heard that was good from somwhere, theres 4 150w gro lights with two aquatic plant growth lights on them. i used a bone meal organic phosphurus supplement,"i just now saw that it was a phos...supplement, not sure what that does." an alaskan brand fish fertilizer and i think thats it. three of em lookin great, only one out of 5 right now have a thick stem, thats another problem, i ve got a one plant who cant even stand up on her own, and saggy leaves, my used to be favorite plant now has saggy leaves, what can i do about that? i know this wasnt written that clearly but i thank you in adavance for your help/advice.

do you have a fan in there for air movement?? That may be why the one plant is so week, needs some moving air to strengthen the stem

4 150w lights? were these CFLs? what were the temps in there? did you let the soil get completely dried out before watering? how did you apply the bonemeal and how much? what strength did you mix the nutes? what kind of soil? too many unanswered questions to make any kind of reasonable diagnosis.....