Hi,

Usually increasing air flow will reduce humidity and vise versa. If you have a speed controller for your fans then you can change the speed, or you can use a timer to turn them on and off every couple of minutes. For little seedlings use a plastic dome for the first few days. Usually when they get bigger you will be trying to reduce humidity, not increase it. The bowl of water idea is good for increasing humidity.

Also, relative humidity is the percentage of water vapour in the air out of the maximum amount of water vapour it can actually hold. The maximum amount of vapour the air can hold at a particular time is called the saturation point. The saturation point will change depending on temperature. Hotter temps will increase the saturation point and colder temps will lower it. So, if you increase temperature, you increase the saturation point, which lowers relative humidity (if the level of water vapour remains the same).

I hope this helps. Look forward to seeing your grow