Orion F1 | first try at F1 strains and dairys

writen on day 7: They are coming along, the roots seem to have formed a bit and they are now speeding up growth. It took them around 2-3 days to come ot of the ground. the talest is 4cm right now the other too 3cm im very suprised how the one who id assume took the most stress so far due to my mistakes seems to be the healthiest one to me (last pic). The biggest one sadly yellowing a bit , and tho i know the first leafes are not really that important i do think it was due to either me not giving her enough nutrients and/or the co2 level were to low to support that level of DLI (daily light intergral). while i think it was more likely a nutrient mistake intead of lack of CO2, i undoubtedly will run into low co2 level issues during flowering if i continue the 20hours light cycle with the MIGRO ARAY 3 LED, probably even at 18. So i either have to cut back on the light hours, light intensity OR perhabs raise the CO2 levels in my tent which i will look into. As far as i know thats pretty cheap to do the more expensive thing is the CO2 measuring instrument i do not have right now but will probably get during this grow so i can push the Orion to space and beyond so to speak. cant wait to see those ladys mature! in case anyone reads this :D and if any of you have expirence with co2 in grow systems, maybe cheap DIY ways to set it up, and or opinions id be glad to hear them. This is my first grow back after 1 year break so some rusty mistakes are bound to happen :D