First leaves already seems to be burnt

Could be a lot of different things hopefully it pulls thru if you have more seeds you might wanna just start new ones for back ups

Get rid of the cover and let it grow normally. You're causing heat stress. When required lightly water around the plant's drip ring, be patient and wait until it comes out of it. The plant grows the way it wants not how you want it to.

Seedlings do not need high humidity..........it is a left over concept from the 1960s when everyone thought pot was a jungle plant. Remove the bag asap, plant will recover soon enough.

Soon as you see green its time to lower humidity, high humidity levels are a replicating of spring showers, once the seedling has broken out its shell and it has its first set of leaves what it needs is oxygen and co2. Oxygen in the rootzones, co2 from the air and phosphorus is the primary nutrient for seedlings upon germination. Co2 consists 0.04% of air, by covering with a baggies your killing the plant, suffocating it, it needs that 0.04% not 80+rh%. At 80%rh all stomata close to prevent seedling from breathing in water and suffocating for lack of better explanation, People don't think of oxygen as a nutrient a plant requires bit it is a requirement in the soil to have pockets of air with oxygen molecules, oxygen keeps a weak bond and is uptake by rootzones for use in photosynthesis. Ideal soil composition for plant growth is shown to have most efficent growth when 50-55% of a medium is pore space, (air). Slightly warmer, slightly drier, this will promote Evapotranspiration and will allow for much simpler watering knowing that the slightly drier conditions alleviate any overwatering. I recommend air pots to completely remove over watering as a outcome coupled with drier environment. This is best advice I'd give to myself if I could go back in time. Once you learn to more of the water cycle in cannabis then look to tweak vpd and negative pressure as you become more confident. Best of luck with the wee ladies. 👍

No picture. Regardless, use a dichotomous key. KiS organics has one for free that is pretty nice.