Are those plants all in the same pot? If they are, you need to thin them out. Your going to wind up w/ small plants b/c the roots are fighting for nutrients.
If you're growing outside, then there's not much you can do about the humidity. But you can do something about the heat. Try putting a...
first stop watering your leaves. Wetting the leaves can cause mold to grow on them.
Try getting rid of your solution all together and making a new one from scratch. Also, check air circulation to the roots.
What kind of lights are you using and how far are they from the plant?
the brown spots are permenant. If the plants are looking healthier, the new leaves shouldn't develope the dead areas.
If on the new growth, there are still brown spots, you might have a disease. Quarantine the sick ones from the healthy ones and clean the area.
I would think that you would need a more rounded fertilizer. Blood meal has no potassium or phosphorus.
The soil should have enough organic material in it already. I would wait to add fertilizer to it until it starts to show signs of nutrient deficiency. Adding fertilizer on top of fertilizer...
You can bend them, but I hear that doing this causes a hormonal change in the plants - that it makes all of the lower branches act like main colas. I'm not too sure about that though. I'll find out soon enough... I just had to bend mine over to save space too.
You can wait till it preflowers, and take a cutting from the plant. When it roots, put it on a 12/12 light cycle. If it's a male, then get rid of the original plant (unless you want a male). The cutting will be an exact copy of the original plant - sex and all.
You can't tell what a plant's sex...