Vpd and temperature concerns for day 16

too low.. RH too high even for a seedling. 77% is too high due to mold risks too. 65% and below is what you want to stick to and avoid temps that result in sky-high VPD at 65%. image search for vpd tables and you'll find a range of recommendation for each stage of life.. .so that stuff certainly isn't well-research to give a very specific answer for the marijuana plant. Avoid extremes, for sure. flip a coin on what you target within those commonsense suggestions you find out there. maybe .7-.9 for seedlings, but then .9-1.2 for mature vege and i see a wide range for flower suggestions, so let's just say 1-1.5 .. i think 1.5 is a bit high but i regularly hit that due to my lack of tight control over climate and seems fine. Remembe,r there is a wide range of suggestions out there... Also, remember VPD is calculated from leaf temp, not air tem. Due to evaporation occuring, leaf surface temp is a bit cooler than air temp. So, your .5 vpd is even lower, which is more concerning than i initially said.

19 is not devestating, but if you can manage to get it up a few more degrees, that would hit the sweet spot. re VPD, there are a lot of personal opinions, but i would say that 77 is just around the sweet spot, but would though try aim for 0.7 (mid 60´s)

I would go with the temperature at least 20-22C. The plant needs warmth to grow optimally.

Hey! A VPD of 0.5 is actually quite fine for a 16-day-old seedling (0.4 to 0.8 is generally recommended for early growth), so you're good on that front. However, what you should adjust is the temperature: 18.7°C is a bit too low for lights-on. It can slow down growth and keep your substrate wet for too long, which increases the risk of root issues. Try to bump the temperature up to around 22–24°C and lower the humidity slightly to about 65–70% to get into a better sweet spot. Otherwise, the seedling in the picture looks healthy and vigorous—just give it a slightly warmer home so it can take off!

I keep my seedling VPD around 0.7-0.9 With a Jogger Rh in the beginning ( up to 75% ) Go towards 0.8 VPD now, she has enough leave mass by now to transpirate properly