You do not have to fertilize your seedlings till at least their third week of life. Your plants look healthy. To me it looks like you have a tight internode length, which is good. Keep doing what you are doing. It is normal for lower leaves to yellow and die when there is hardly any light reaching them.

Do not add moisture to your grow room. 40% RH is good for veg and will only rise when they are in full bloom. Then you will be trying to lower humidity. Whatever you do don't buy a humidifier, get a dehumidifier if anything.