Shiny leafs, then folding, dry tips, very few rust spots. PLEASE HELP B4 it's to late

OK I'm new and 1st want to thank the site and its most helpful members. I have Golden Seed, Fem. Blue Monsters. I use a simple concrete mixing tub full of Hydroton with a drip and drain that turns on twice a day for 15 minutes each time, and use Technoflora Nutrients, and a 600 Watt MH for Veggy time. I am around 6 plus weeks into it, and have pre-flowers. A few weeks ago it started with the lower/older leaves going shiny, and then they started to fold up kind of like Tacos, and then now I have some dry tips and edges, along with a few small rust spots, plus a little bit of yellow spotting.

1st thing I did was flush the system for a few days, and it only seemed to stop them from getting worst. And since then I have only used a very weak Nutrient solution. It seems to have days when they look a little better, and then they go back down hill.

I know we have hard water. I do adjust the PH to 5.5 to 7, as I have been trying to figure out whats makes my girls happiest. below are some pics of my girls.

Please Please Please Help.
Thank you Massburnout from the east now living in the lap of the west.

If you are flooding and draining them in hydroton you should be doing it three times daily for the 15min cycle. I never go over 1/6th on what the ferts recommend in my mix.

Have you got high temp and low RH? The leaves look like they are trying to conserve moisture. Low RH can effect secondary nutes.

The room has good ventilation, and I run the lights starting at 6pm till 12 pm to keep the heat down.(heat wont be an issue for me until after March) So I'm sure it's not to hot, at times I suppose it could be a little cold if there is a temp. issue. I noticed the 2 in the back that are more likley to be coldest and are affected the most. I am embarassed to say that I don't think I know what RH is. I would venture to guess it is an abbrv. for one of the elements that we look for in our nutrients, at risk of futher embaresment.

Thank you so much, any further info would be great.

Relative Humidity

That looks like magnesium deff to me. Cold root temperatures or hard water can cause your plants to stop taking in magnesium. Im not too experianced with hydro but IMHO your plants look like they have a ph issue or an early stage of Mg deff.
Try figuring out a way to get your temperatures more stable. Most problems with indoor growing stem from improper nutrient ratios due to PH fluxuations and/or environmental stress.
Proper temperatures and humidity play a pretty big role in growing healthy looking plants. (FYI, RH stands for Relative Humidity)
Try to never have more than a 10 degree temp fluxuation.
Your plants will take in most macro nutrients aslong as your PH is stable and there is enough light, while improper temperatures and humidity levels tend to affect micro nutrient uptake which can make your plants look sick, but since NPK plays a bigger role in development, micro nutrient deff usually wont screw up your harvest too bad aslong as the deff are minor and your grow room temperatures are stable. More times than not if your using a good store bought 1 or 2 part fertilizer and your growing hydro, the problem is related to temperature fluxuations and high or low humidity levels, or PH and hard water issues.

Try putting some sort of insulation like carpet foam, carpet, cardboard boxes, ect.. between your pots or res tank in efforts to seperate the cold floor from your plants roots IF temperatures are too inconsistant. Since you have your plants in a concrete tub, you might try adding a little space heater that automaticly turns on or off to help stabelize your temperature levels.
BUT, If your temperatures are ok, then your problem is PH or Mag related.
If your using reverse osmosis water add Cal/Mag, but If your using tap water just add epsom salt as most tap water has alot of calcium in it which can lead to a magnesium lockout (which is what I think your problem is).
My advice for right now: Change your water and cut it with a 1 to 1 ratio of reverse osmosis to tap water to bring down the "hardness" of it.
Next, get your PH dialed down to 5.5 and keep it there! (dont let it change from 5.5 to 7.0 as the fluxuation is too dynamic for hydro and will cause problems.)
Then, add a flat tablespoon of epsom salt for every gallon of water you use.

From now on stay consistant! Since you have hard water, cut your water with a 1 gallon to 1 gallon ratio of tap water to reverse osmosis water and add Cal/Mag to every watering and keep your PH at 5.5-5.8 from now on.
Hope this helps

Thank you so much everyone, especially GreenChile. I just flushed with Flora Clean and put some distilled water in, with a weak nutrient mix. I'm going to make the mix a little stronger, because this is clearly not nutrient burn.(thank you guys). And I'm going to get my res. off the cold concrete floor. Isulate as best I can to get a consistant temp. in there. Then once the use of distilled water proves my water issue, I will start filling my res through my faucets brita filter and add epson salt, to the tune of a teaspoon per gallon.

Ok I am in a very dry region of gorgeous SoCal. just moved here 3 months ago, and I love it. I already keep the top of my res. open to try and add some RH(again thank you guys) and I add a lot of water and keep it PHed and on hand days in advance because of it. So now what else can I do to add RH? I have a swamp cooler but I'm afraid that would make it to cold this time of year still. If I put my power strips behind my poly film walls, would it be safe to run a mist pump, if so how many times a day, and if so do I need to use distilled water in it?

Please and Thank you guys. Oh any info on what kind of commercial lisenceing I need in Cali. to grow enough to sell to dispenserys?