First Grow, Did Lots of Research but Still Major Problems! Lots of Pics, Please Help!

Hi guys, I’m new to growing and to Rollitup (as a poster, at least), but I’ve got my first grow going and I wanted both to share it with you guys and to get some help with some issues I’ve had so far.
As I mentioned, this is my first grow, but I’ve put a LOT of time and research into preparing for it, and I’m trying to be as thorough as I can without going completely all-out.
Right now I’ve got six plants, all grown from seed. The plants are about two months old from germination. Four of the plants are high CBD Sage n Sour, one is an MK Ultra and one is a Kali Mist. Some more info about the grow:

• Growing Indoor
• 400w MH light in a sealed and vented hood
• Plant age: 2 months from seed
• Consistent 79-81 degrees F with 30-40% relative humidity, temp drops to around 65-68 with lights off
• Growing media: Sunshine Mix #4, unamended
• Watering schedule: approx. once a week, using tap water (tested @ 165ppm on TDS meter, 7.2 pH)
• Nutrients: Earth Juice Grow, Catalyst, Microblast and later Hi-Brix Mollases 5mL/gal. each, applied approx. once per week through a nutrient tea that’s brewed for about 2 days.

Alright, so my plants were doing great up until just before the third nutrient application, which was about two weeks ago now. Shortly before that nutrient application, we started to have some problems. The bottom leaves of the MK Ultra and a couple of the CBD plants started to yellow, especially in between the veins. Here are a couple shots of the MK just before the third nute application. You can see that it looks pretty healthy overall, but the yellowing between the veins is starting. It was more obvious in person than it looks in these shots. I don’t have any shots of the CBD plants from this time, but they looked the same as the MK Ultra:

I did some research and found that yellowing between the veins is a sign of magnesium deficiency (which additionally made sense to me because I didn’t have any dolomite to mix into the soil even though the instructions I went off of called for it). We took some USP Epsom salts that we had on hand and mixed them up @ 1tsp/gal. in a spray bottle and sprayed the plants just before the lights went out for a few days.
The Kali Mist plant at this point looked better than the others. Its bottom leaves were showing some slight yellowing (hard to see in these shots) and its top leaves were curled up a little, but other than that it seemed okay. It got a foliar application of the Epsom salts as well, but only once or twice compared to I think four times for the other plants. Here is the Kali Mist at the start:


Five days after these photos, the Kali Mist was having the worst problems. The bottom leaves were mottled with necrotic brown spots. Most of the spots were in random places on the leaves, but one leaf was dying from the tip towards the middle. The plant overall was droopy. The bottom leaves were continuing to yellow. The stem was streaked with purple and the petioles were turning purple. Here it is at that stage (the purple stem shot is actually from later when it was even worse, but you get the picture):

As this progressed, the Kali declined at a steady rate. Here are some progress shots of its downfall, over about 5 days:

Over that time, the other plants have been getting worse too, but they don’t show all the same symptoms. The MK Ultra sort of stabilized for a while, then it started down the same path as the Kali with necrotic spots on the leaves that start at the bottom and move up.
The CBD plants started to show a mottled purple “bruising” on the bottom leaves., and then recently they’ve started showing the spots too. The pictures here show the bruising pattern well, but the color is much more purplish in person than this shows:

They've also started getting the necrotic spots on top of the brusing:


And here’s the MK as it got worse:


Okay, so all of those pictures out of the way, here are the things I did that I think potentially might have caused it. Basically these are the only areas in which I’ve strayed from the way everyone says you should do things:

1. Before I applied the 3[SUP]rd[/SUP] round of nutrients (the round that came right after the initial set of photos), I didn’t have any organic pH adjusters, so I applied around 1mL/gal of some rice vinegar that I had to some nutrient tea and was surprised that it was more than I needed, bringing the nutrient solution to a pH of 5.6. I knew that pH was low, but I also knew the growing media was a little high, and I didn’t want to waste the nutrient tea I’d just brewed so I went ahead and applied the nutes. My runoff pH to 6.2, obviously on the low side, but I didn’t think it was low enough to cause anything like this. In retrospect, this is the biggest example where I “strayed from the path”, so I think I could’ve shocked the plants with a wide pH swing, but if so, why didn’t they start getting much worse until 5 days after applying the nutes? Why were they also starting to show symptoms before the application of the nutes? Beats me.
2. I didn’t use any dolomite lime or worm castings in the original mix like the instructions I followed called for. We tried to supplement magnesium through the foliar feeding, but with all the other issues the plants have had I don’t think this is just a magnesium problem.
3. Our tap water might be bad. We’ve noticed that our “humidifier” aka bowl of water that we leave out is also filled with tap water, and when it all evaporates theres a LOT of residue left in the tank. Not sure if maybe that’s building up in the soil and causing problems. I tested the tap water with a TDS meter @ 165ppm, so it doesn’t read as being too bad, but it’s possible I suppose.

I’ve got some dolomite and worm castings coming tomorrow, and I figure that whatever the problem is, there’s something bad wrong with the media they’re currently in so I’m planning to transplant them to bigger pots. I’m planning to mix in some dolomite and worm castings with the Sunshine #4 Mix, and apply EJ Grow, Cat, Microblast, and Hi-Brix molasses at 2.5mL/gal., and some Hygrozyme maybe as well. Also planning to use some spring water from the grocery store instead of tap for the time being. Does that seem like a decent plan to you guys? What do you think is the ultimate source of this? I’ve tried to grow with close attention to detail and without making the newbie mistakes of overwatering or overfeeding, but obviously I’m still doing something bad wrong!
Thanks you guys so much for your help and also I’m planning to put together a full grow log showing more of our grow tent and the progress of these plants as they either recover or we start a new batch if needed, so be on the lookout for that as well. =)

Sorry man i don't have the attention to read yur whole post, but lookin at the pics n what medium ur in, I'm gonna lean twards under fert, try bumpin your nutes, or let your soil dry out more between waterings

seems pretty complicated for a first grow,but i grow in soil only so what do i know,lol,the plants look pretty sick,hope you get some good info,

I only looked at your Pics, too.
I agree under feeding.
looks like a (P) def, going on. leaves are pale green, they should be greener.
don't over water. just moist soil, only when she needs it.

Good Luck on your Grow.

Those are pretty small for 2 months old, definitely something has not been quite right for them.

I say just start all over man, 2 months old not worth the time and effort for your rewards

Fair play on posting all the info required and good pics to boot, and you have obviously done your research because the first thing I though of was a cal/mag problem

If there is a residue left behind from the water it could be a sign of high cal levels and this is locking out the mag, although at 165ppm your water doesn't seem to contain too much mineral content.
Maybe the ph of the soil is creeping up over time and causing a lockout?
Have you tested the ph of your feed/tea?

your pots are too small for 2 month old from seed. many different nutritions seems to be locked. Transplant them into bigger pots. no matter if the problem is PH related, overfertilization, root bound, deficiencies etc.
a transplant should fix all your problems.

Also i would like to add that when the yellowing starts in the lower areas of the plant is a indication of N def. But there ca be many reasons. Honestly im surprised you diddnt run into problems sooner after 2 months in such small pots with only tap water. Listen to the plant and don´t waste too much time with nutrients and mesurement.

Around 4liters of soil per month of growth is a good rule of thumb.
A good idea might be to give them a good flush before transplant.
Your problems should be solved rather quick with a transplant in my oppinion..

And dont throw away your plants. even if they are a bit small you still have 2 months worth of age (they will show sex soon..) and roots.
Transplant them and just let them veg until you consider them as fine. worst case scenario you could still clone them fairly easy.

Those plants are nitrogen deficient. I would up there grow nutes and drop the hibrix. Excessive calcium can inhibit the uptake of many elements.