howz it going! first off, you have a good setup there with the light exhaust venting and the tray size. I will compliment you on the hydro tent and also the health of your seedlings thus far. They are looking healthy but also needing a few additional things for the future. It sounds like you have a good general understanding of the basics but let me give you some tips / opinions.

First, you mentioned that you have a 3x3 tray for all your plants in hydro. This ok, but for the number of plants you are trying to grow it is not. You didn't really mention how much vertical space you have to work with so with that in mind, I am going to assume you have enough for them to get to a relatively good size.

You have too many plants to produce a good size yield for a 400W hps light. I made the same mistake recently too in a 2'x4' tray by having 10 plants. You said you are trying to go for 14 plants and this is too much. If you want to produce higher yields, grow fewer plants so that they can take up more nutrients and also have more light. Less plants that are bigger will produce more yield than more plants that are smaller. I would recommend something like 6-8 for your setup.

You have the right conditions, just let your plants have the highest chance for survival and also big yield where ever possible. Your humidity issue is not a problem. In veg state anything over 90% is a problem. Until then you can stay in your 70%-80% range without any worries. Also, you never made mention of your temps in your room but you did state that they were of concern to you. The same goes with temperature, you can push it to about 85F or 90F but past that is again, trouble.

The other problem I see which is a big problem is the fact that it doesn't appear that you have your plants in individual containers. This is going to be a huge problem when they begin to flower or even when they begin to grow large during the veg state. What will happen is the roots will grow into one another causing a competition for nutrients and also causing them to tangle up inside the medium.

For your setup I recommend immediately:

1. place your pots individually into small to medium sized mesh pots that allow the water to come in on all sides and make sure the holes are big enough for roots to grow out of.

2. remove the tin foil from the rockwool of your plants. Tin foil (especially crinkled) will cause hot spots of light on your fan leaves. Not only that, but the undersides of your leaves do not need light as they do not photosynthesize. Additionally, if you are trying it to keep the light from hitting the roots, I wouldn't worry about that either since the hydroton does a pretty good job at that.

3. Kill off some plants. I recommend weeding (no pun) out the smallest and least healthiest of all of them. Again, do not hinder your veg growth for the sake of having more plants. Let the healthy ones that ARE there get bigger than they could have before they had the space around them. Take a look at my setup and see that growing too many under a 400W light is not necessarily better than growing the right amount. We have 8 now and plan on going with 4-5 for the next grow with hopefully higher yields.

Hope all this helped.