Thansks for your replies. Well, I went ahead and used a tsp of calcium hydroxyde on each bucket. Tomorrow I will measure the ph. What I observed until now, is that a bucket with three plants (the ones from the pictures) are showing something different. The tops are a little bend down, but just a little. And one of them has two lower leafs a little soft. I think it's not good, but I will tell more tomorrow after I measure the ph. Maybe it's overwatering, since I used a lot of water after the calcium hydroxyde. The thing I am scared is maybe I raised the ph all of a sudden, and I read that it must be raised 0.1/day. Maybe they are stressed and need some time to recover. If they are indeed males (I also think so) then no big deal about it.
I will deffinitevly get some Lime, but I don't want to order it online. It's not about the cash, I just want to sleep well at nights. This round is almost over, but I will prepared next round.
I have one more question about temperature. The ideal temp is 21(70f)-26(80f) celsius, I read about this. My question is, where should one measure this temp in a grow box. Meaning, if you measure at the top of the plants, it's very near the light source (heat source) so the temp will be higher. If you measure near the ground level (roots level), of course it will be much lower. So I guess the best to measure it somehow in the middle of the plant, but I need your confirmations.
Regarding ventilation, let's say the outside temp is 18C(64f) can the intake be direct on the roots level of the plants. On my setup I used a duct to direct the air at 90 degrees down, and I made some small holes into the duct to send some week air curents to the middle-tops of the plants (if the ecurrent is not blocked by leafs). Is it ok? or I should let the air current directly on the lower side of the plants, with the whole power. This will help me, because the strong current will cool down the box, the fan will be off when it's cooled, and the CO2 generator will be used. (I plan to use some diy generators, with sugar, water and yeast, I read about them in a book).