Autoflowering Sweet setup needs help

Hello to the Rollitup community!

In advance: all my units are metric and yes, this is my first grow!

I have 5 Sweet autoflowering seeds planted:
2 Sweet Fast Bud
2 Sweet Speed Devil
1 Sweet Big Devil


My grow area is about 60x60x200cm, surronded by 3 white walls and a silver foil wall,
in a room of 3x1m with no ventilation, although I occasionally leave the doors open for a breeze.
My lighting is one 90W UFO LED with 24/0 lighting for the vegetative period and I was
thinking 18/6 or 20/4 on flowering period.
My pots are 3L (Liter), which I thought was enough for autoflowering which grow usually
40-80cm, with the expection Sweet Big Devil was promised even to 1-1,5m.

I water my plants every 2-3 days with tap water, which sits usually atleast 24h,
and watching the humidity in the soil every 1-2 days.

Before I planted my seeds, I mixed chicken shit and sand with black soil as a fertilizer,
flushed it with water and let it sit for 2 hours, then planted the seeds and put them
under two 20W regular lamps because my still awaited light hadn't arrived when supposed to.

Only a week later I got my real light but two seeds had already sprouted with the regular lights.
First one of the Sweet Fast Bud seed started to grow, although at first not very quickly,
but with the other 3 seeds there seemed to be some problems.
The second Sweet Speed Devil started but very slow and near to the soil.
(My thought was that maybe they were growing their roots).

The first Sweet Fast Bud to sprout got itself going after being 3 days (but total 10) under
the UFO LED and got quite a bit ahead of the others.
The second Sweet Speed Devil came along also after half a week
but the two behind did not show signs of life a lot, after 3 weeks had passed,
I decided to plant another 2 seeds to replace the ruined ones.
As I also had one seed over now, I planted it to a smaller 1L pot to see how strong
could it grow and I knew that because I planted it a month later of the first two,
there would free some space up anyway by that time.

Now at week 4 my first Sweet Speed Devil is 23cm, Fast Bud is 21cm and the second Fast Bud is 13cm.
The second Big Devil has been planted 1,5 weeks ago (approx.) and should any moment now
spread it's first leaves but the last Speed Devil is still a seed in the 1L pot, although it was planted
about the same time as the Big Devil. I have a doubt that I haven't watered it enough, as being such a small pot.

A few weeks back there was a big confusion and I tried to take care of my plants the best but because some
of the seeds didn't go so well in the beginning, I mixed up something in my head and didn't count
when I planted the 3 other seeds, after those first two.


Now to my question and problem:

At first I started to notice some small white/yellowish leave end in the bottom of the first Speed Devil
but the plant itself seemed healthy overall.
When the other plants got bigger too, they didn't have such problems but when time went on,
it started to appear on the first Fast Bud too, but on a smaller scale because for the Speed Devil,
it has gotten worse and to the point where I need help here or it could be bad trouble.

Also there are some thin leaves and leaves curling.

I am right now thinking over again the idea to use different nutes as I am not still pretty sure what they exactly are
and where to get them but it seems I cannot be without them in a indoor grow.


The first Sweet Devil and Fast Bud are both smelling good already a week and I suspect them to start flowering soon, although they aren't very big still.
My theories:
1) I have watered the plants too little as the average temperature in the room is 24.5C
(but I have heard the talks about better to water them less than to flood them)
2) I haven't given them nutes which I know little about
3) My light is too close/far - I usually hold the light 10-15cm above the plants but now today set it to 25-30cm
as all the plants could have a wider spread of light and also all the plants were growing a little tilted towards the LED.

I haven't had much too good personal advice, I have read a lot of grow journals and grow tutorials and then experimented and giving love.

Thanks in advance!

(ps! photos show curled and dried leave ends, but notice that the dried leaves tend to be the most bottom leaves
and the upper parts seems healthy but I fear that it may spread up and needs help)

u need to give them some food u r starving them and ph ur water b4 feedeing so ur ph dont go crazy on u

Thanks for the replies, although could you be more specific?
What do you mean by food and how much of it?

I'm not too worried about the pH level, although I should get a pH tester,
but if you mean starving them by not given any fertilizers, it may be true,
although in another long grow journal I read yesterday of another autoflower grow,
the guy gave atleast 4 weeks for the vegetative period without fertilizers.

(not sure if fertilizers = nutes)

You need to give umm some nutes bro, fair enough you are probs watering lol..yeh but the fact is they do like more than just water *nutrients = food* *food = nutrients* remember though autos are very sensitive to nutes so start on a LOW dose..

I found a shop in my location where I can buy nutes but now am wondering which ones.
I understood that the main ones are N P K and my options are:
- PK 13/14
- N 27%

and then there are different Bloom solutions available.
Both the PK and Bloom solution are said to be for flowering period only
and as I understand the nitrogen is for vegetative but is it correct then that
I will only use N for the vegetative period?

Also when can I be sure my plants have started flowering?
because already 2,5 weeks in the first plants started to smell
a little and now as the others have too and the first one has gotten bigger,
they smell quite a lot for a 4 and a 3 week old plants.

Thanks!

*the underlined parts are my two question*