First grow....HELP

hey everyone....this is my first post....ive got 6 seedlings growing in an un-used fish tank under the light...... first of all is this ok???
they are quite tall and weak looking...... they are also getting quite tall before the jaggy leaves start to move away from the first two leaves...... i had 8 planted but 2 just simply fell over....it was as if there was a kink int stem or something so i just tossed those two...... one also has like a white powder or something similar on the leaves and the first two leaves that formed(not the hash leaf shaped ones) have started to go bad round the edges..... Any advice at all would be greatly appreciated.

They will be stretching towards the light mate, i dont think a fish tank light will be stong enough to be honest, if they are looking really stretched get some deep pots any bury the stem nearly up to the first set of leaves and move them closer to the light.

As for the white stuff, im guessing it will be some sort of mold or something, do you have any ventilation? All the best

i have a fan that i sit in the slot at the top of the tank but i haven't been doing it regularly to be honest.... i have been leaving it with the lid on most of the time..... should i leave the fan running the whole time the light is on??? thanks for your previous advice.

Also i'm planning on putting them in my loft under a 400w hps light in a make shift grow room(closet really).... But im worried about it getting too cold when the lamp goes off.

plants love light ,fresh air and fresh water the more of those you provide the happier they will be sounds like the light your using now is not enough lumens to make strong healthy stems wich provide all the nutrients to the plant and the white powder is probably powdery mildew your plants being in the fish tank cause a greenhouse affect causing very high humidity in the tank witch also is causing the white dust"powdery mildew" on your leaves the fan will not only prevent powdery mildew it will make your plants stems strengthen up from the wind and it also provides circulated air if you can set up that 400 wt light now better than later your plants will love you for it and if you want results 1000k watts is the way to go not here for along time just a good time peace

i was thinking about putting them under the big light but i thought because they are so young i wouldn't be able to put the light close.... would they not stretch more towards the big light??? the plants are just about two weeks old, 4-5 inches tall.... thanks

thats them re-potted much deeper.... just hope they survive.... i have got the light about 25 inches away from them.... is this ok????