Why is my auto so small?!

I have a Auto la diva afrodita growing as my first grow in a room closest in a 5ltr pot with 400whps keept 15 inches away with a fan blowing gently over the plant.
I'm useing john innes multi purpose compost with 10% perlite i let it grow and do its own thing for the first 3 weeks and watered when the pot felt light it was still kinda small though for its age, so i added a CFL bulb which gives of only 800 lumens right above it with the hps shining on it. Woke up one morning the light burnt 3 leaves making half of what it was lent on crispy, so i took the crispynes of and noticed that the plants growth stoped for about 3-4days.. It's now 36 days and the plants only 6inches tall with short branches.. i added a 1/4 strength of tomatoe fertiliser NPK 4.0 3 8.0 on its last watering which was yeserday, their are small pistols shooting through the top but the plant its self is still really small! here's a picture of the plant, any idea why its so small and anyone got a rough idea how much more it might grow ? I've noticed over last week it's grown alot (4-5 days after the burn which happen on day22) it really confuses me because the plant is healphy nice green leaves yet still so short! Maybe it's my PH level of soil ? I don't have anything to check the ph level but does this stunt growth alot yet the plant looks healphy? Or maybe i've just got a runty seed, the seedbank i used was herbieheadshop via dianefem i got a white widow fem which didn't even come out the seed, waited 12 days! the afrodite came free with it, thank you for reading!

anyone? please

auto's are always small you will never get a pound off a auto

i dont know about autos or jonny soil i you a 400 watt also i use miriical grow potting mix and they grow fine i have a hydro shop about 1/2 hour an i still dont buy there fox farm and other soil to much i think i do use nutes after a while because its not desine for reefer i think it is to late for your plants if they are autos there flower on days not maturety put hand on top of plant put light till its feels good not to hot that will be good

i wasn't expecting a pound? i was only asking why it was extra tiny for 36 days, everyone else's seems to be 2-3x the size of this at 36days.. looks like im gonna get 1gram at the most haha

by the size of what it is, how much bigger you think it'l get ? does it tripple in size when flowering? it only started flowering like 2-3 days ago like the first signs.. ah yes miracle grow i have, i might do a grow with mircale and one with john innes mixed with perlite and compare them, only thing miricle grow can nute burn early on so do you transplant them in after 2 weeks? yeah the tempeture of the top is fine, the fan keeps it cool

regaler plants get about 1/3to 1/2 size bigger when flowering

I think the light is too close, i think the pot you have is too small for good root growth, and good root growth is fairly important for the growth of the plant.
My Auto's at three weeks were about 8-10 inches tall then they just blasted upward. one is roughly 20in (bubblelicious) and the other id say is scraping 2.5ft. (AK49).
my 400w HPS is about 20in from top of plant.
You keep burning the leafs and shocking the plant, you'll sacrifice overall yield.
And if you're burning the leafs then there can't any humidity; It is important to have humidity around 40-50%

Also, do you have a fan blowing through the leafs? Air circulation is important for growth too. If you don't have constant flow over the leafs, there will be a lose in co2 and o2 exchange through the little atmosphere surrounding each leaf.

Don't over water, and don't overfeed... this could also stunt growth.

Also, the plant will shoot up and stretch once full flowering begins.

I think it may be the pot and the fact the light feel on it and burnt a few leaves, most probally shocked it real bad then then roots hitting bottom most probally just made it even worse, i've got alot bigger pots but i only got them yeserday i figured it would be to late to transplant seem as it's flowering.. want me to put a pic up of the plant in coulple of days to see what its progress is like? from your personal expearance the plant being some what 36 days old, whats a rough yeild you think il get at the very most it's 6i tall atm but you can see in the pictures.. yeah i have a fan blowing over towards the exit of the closet.. i'll move my hps further away too, hopefully it'l stretch a little ?

light is too close. they are stunted. auto's life cycles are so short that they will not be able to bounce back and your yield is probably cut in half. for seedlings and especially autos start that light out at a good 24 inches and lower if needed. I keep my 400w about 16in away and thats with a cool tube. goodluck bro

ohh okay that may be the problem as well thanks mate, and thanks to everyone else who write on this.. i'll keep in mind everything which was said to me, not sure if i should get some more autos i can grow maxium 4 in the space i've got.. what you think ? 4 autos or 3 regular fem if so what plant would be good for beginner but i desire big yeild ha ha any easy but nice grow strainss & cheers man

the pots i've got are 9inches from top to bottom wth drainage holes, god knows how many liters it is it don't say on it haha its basicly double the size of my other pot which was 5ltres

1 last thing may i add is it okay to mix organic fertiliser with a chemical one (organic being bio bizz bloom ) (chemical one being tomatoe feritlizer if not should i use the oraganic bio bloom npk of (2.5) (7) (4) i figured the oragnic would overall be better then chemical also i have cannapk 13/14 comming tomorrow, when should i apply this ? tips please, i would be very greatful!! thank you once again!