You know I really dont see a problem at all....

THose brown spots on leaves can be caused by the leaves dipping on to the dirt, or water or soil getting splashed on them. Those leaves will be long gone anyhow once it starts.

I would say:

1. Try to lower your air temp. I am not sure about all the extractor / intractor whatever that means. Remove the hot air thru a vent and blower fan.

2. Don't worry about the humidity at this point....

3. Water with a pH of 7.0 - 7.5..... that soil seems a little bit acidic.... 5.8 is just too low. Buffer it up with the adjsuted pH range.

4. You dont have nute deficiency. Very hard to have so early.

5. Water a tad bit more often. And water the ENTIRE soil base.

Remember, you are entering the critical phase here, weeks 3 and 4 when the sex will most likely be determined. Don;t stress them from heat and not enuff water. Too much is better than none in my opinion at this time.

Looks good, I would relax and let them grow.

HARD ON