Help fix my grow/confirm my suspicions

New to posting, but I have been reading a long time. I started growing a few summers ago, and things have gone from scrawny and tense to potent and satisfying in the time that has passed, much of which is due to this forum. I started growing for my aunt (in her 70s) and my mother (55, just had knee replacement surgery), and most recently am also growing for my fiancé...and of course, for myself!

Sorry, I'll get to the point:

I have a 4 foot by 5 foot by 2 foot (8 sq ft base) tent with a large fan (I live out in the middle of nowhere...truly no need for odor issues, in a state that will have legalized it by this November without any doubt [I am up to date on the polls]) for ventilation. Right now, I have 6 5 gallon pots filled with a mix of soil, perlite, coco, and all sorts of good bacteria and such (I could be more specific if you think it is necessary), likely not the best soil ever used, but specifically for indoor growing.

With summer temperatures reaching 83 degrees in this cabin so far, the plants have been, well, growing like weeds. I water every 5-6 days (when the soil is dry and they start to droop), though this soil mixture really retains a LOT, as achieving a good flush has been problematic (next watering they will get a gallon each to see if that will produce a flush...)...there are definitely holes in the bottom of the pots, and as for drainage, I have crushed up plastic water bottles at the bottom of the pots (in a twisted and irregular pattern).

The lighting is a 400 watt MH, to be switched to HPS upon flowering.

Okay, as for the strains, we have 2 Afghan Kush x Skunk, 2 Blueberry, and 2 White Widow (autoflower). Now, what's great about this tent is that the autos I have grown in the past never grew big enough for me to worry about them getting too close to the lights...of course, now the WWs are the tallest of the bunch by far...maybe it will be just right, but if not, I might look into some growth control methods (training).

Okay...as for the problem...I planted these on June 10th (it has been 25 days counting today, July 4th). As of the past week or so, I have noticed the beginnings of sort of pale yellow rust spots appearing, and while I am thinking magnesium (and I have Epsom salts), dosing worries me, especially since I am not sure I am right. Somewhere after week two, one of my Blueberries had a peculiar sideways-turning leaf (I have since stopped using tap water).

Also, NOTHING but water has been given so far.

I will post pictures momentarily, thank you all so much for the assistance. Hopefully one day I will be educated enough to help other people on here, too.

You stopped using tapwater so you started using RO? That combined with the age of the plants and having given it only water so far, and the symptoms you describe likely means you need to start adding nutrients. Tapwater usually contains a good amount of Ca and some Mg which you need to supplement if you stopped using tap.

Calmag deficency...dont be flushing your plants if you didn't feed them yet ..your only starving them more by flushing With plain water..always flush your plant with your desired ec added.only ever flush with plain water at harvest time or if you over feed them...i never flush in soil..i just leave 20% runoff after each feed that will flush any unwanted salts from the root system..hope this helps..

Okay, here are the pictures:

First, there is the growing area (also, light is on approximately 20 hours a day). Second, a WW auto on June 26th, and then on July 4th (today)



Below, the leaves are turned due to the fan.



Next is the Afghan Kush X Skunk that is beginning to develop some of the same symptoms that are already more pronounced in the Blueberry, and that are currently least pronounced in the White Widow.



Here is the most damning Blueberry:



And here is the quirky one:



Again, nothing but water, light, and air has been used thus far.

Can we get a diagnosis?

What should I do to make sure that most of my leaves continue to be green and healthy?

Wow, thanks for the fast replies! Would you suggest I switch back to tap? This is very helpful, thank you. Perhaps, switch back to tap, and if things don't improve, begin to supplement directly?

Any additional critique/criticism/advice regarding my setup is also totally welcome - again, thanks a lot =).

Start feeding on your next water and keep an eye on them. Think they saying they're hungry.

some of it loos like water was on the leaves and the light got magnified an burned it.

You people are restoring my faith in humanity - I have given them a moderate feeding to test for sensitivity (I put 3/4th tsp into a 3 gallon jug, and the directions called for 1/4 tsp per gallon when fed weekly), and will be feeding them more going forward. Also, good tip regarding the water on the leaves, I'll cut that out, too.