What can I do about stretched seedlings if I want ...

You can do it , but the final result will not be good. 30 days under a dome means 30 days with 90 to 100% humidity , if they survive to that then keep a clone for life as you'll have a killer strain.

Don't waste your time with peat plugs and the like. Start your seedlings in large solo cups or even 1 quart pots. No nutrients for first 10 days. Water only. Water them sparingly like you had them in a tiny cup don't soak the entire cup/pot. Up-pot them when you see roots come out the bottom of the pot. Lighting- start off with 18-20 hrs of light but not too intense. When you see the first true serrated single leaf pair grow lower your lights. If they are stretching lower your lights. The only true way of knowing how close to set your LEDS is to buy a PPF/PAR meter to properly measure the light intensity. Check out my current Blackberry grow week 2 for explanation of PPF/PAR meter intensity recommendations. Hope this helps.👍

They are stretching for light. I would lower your grow light.

leave them in soil for now its easier bring the light down like 2 cm from the dome if you not using a light get 2 cfl 150w they work great keep the dome on and and support to each one be rely careful whit touching them they are extremely fragile at this point

30 days for what? Your roots have stress certainly :/ Transplant to 1L pot in 1 week at 1 month, I think this is better Good Grows 👌

As my other collegues alread mentioned, the girls need to be tansplanted soon, And the closer you get the light to the Girls, the shorter they stay.... So look where is the point of your lights, where they dont stretch to much, and not getting burnt by the heat of the light or the light by itselfs. I go for my seedings with 2x26 watt Led Lights, and put them very close to the plants around 10 cm.... so i can let them for around 3 weeks, alwys adjusting the space between lights and plants. If one is shooting you just can dig them alittle deeper in the pots. And giving them anice airflow helps them to get fatter stems while growing. You can shake the stems, to help them to produce solid stems ( little break appear if you shake and they develop amuch fatter stem. I just take them between 2 stretched fingers( like acigarette) and shake them. To your dome... look that the dome is not completely closed. You risk fouling plants. I give my girls an " open dome" for around 2-3 weeks if its impossible to let run a humifidier. So keep strong and happy growing

They need to be transplanted as soon as possible! They will only stop stretching if they are close to a lie watt bulb. I keep mine for a week under cfl 82w and when they look like yours they go in their final home in the tent.

You could throw them under a light that I'd put closer to that dome so as to not induce anymore stretching in those girls and God why would you want them into those pellets till 30 days they will have issues with everything by that point my friend ..you need to put them into their forever homes anything that is bigger then that . You have some really nice looking girls do that transplant don't waste these beauty's lol transplant ....

You can put a small 6500k cfl bulb about 6 inches above then to stop the stretch, but those seedlings wont make it in those pellets for 30 days. I see roots coming out of the bottom of them. They should be transplanted now if you want to get them to their full potential. They will grow slow and unhealthy if they stay in those starter pellets. Hope this helps.