5 weeks into flower and having issues. PLEASE HELP!!

This is a DWC grow w/5 gallon buckets. I've had pretty good luck up until now. I recently discovered my PH meter needed calibration, my babies were @4.8ish for over a week. I immediately flushed and went back to the 1000ppm GH 3part they had before. I saw signs of nutrient burn instantly so 3 days later I flushed again and went down to 600ppm. It's been close to a week now and the leaves continue to spot,turn brown, and die. Nutrients continue to increase and PH is still drifting lower. The roots are also very healthy. The strain is Barneys Vanilla Kush and flowers for 9 weeks. Please help me save them!

Grow temp 77/48%
Water temp 66
400w HPS
RO water w/1.25ml calimagic per gallon in addition to GH nutes.

I can't upload any pics at the moment, server error, but some good old fashioned brainstorming until then would be appreciated.

Pics are here:

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Good update with the pictures. Have you checked for any bugs under the leaves?

If the pH is drifting lower, maybe there's something wrong with what's inside the DWC bucket...

Not a hydro expert, just trying to help...

-Lay

K , Cal/Mag you are lock Locked.
Any Chemical/Organic nutrients that have potassium in them will fix a potassium deficiency. Peters All Purpose plant food 20-20-20, will cure the potassium deficiency , Miracle grow Tomato plant food, Miracle grow All purpose plant food.( Only mixing at ½ strength when using chemical nutrients, or it will cause nutrient burn!) Some other supplements of potassium are: Wood ashes, which are fast absorption, Kelp Meal, which is medium absorption, Greensand, which is slow absorption, granite dust, which is slow absorption. Sulfate of Potash, Sulfate of Potash Magnesia, Muriate of Potash, which are medium absorption. FOXFARM GROW BIG HYDROPONIC CONCENTRATE, which is fast absorption. (FFGB can bring your ph down as well) Earth Juice Meta-K, which is fast acting. (Can bring down your ph as well) Leaves will never recover, but the plant will show recovery after about 4 to 5 days when using a fast acting nutrient.
Any Chemical/Organic nutrients that have Magnesium in them will fix a Magnesium deficiency. (Only mixing at ½ strength when using chemical nutrients or it will cause nutrient burn!)
Other nutrients that have magnesium in them are: Epsom salts, which is fast absorption. Dolomite lime and or garden lime (same thing just called different) which is slow absorption. Sulfate of Potash, Magnesia which is medium absorption. Worm Castings, which is slow absorption. Crabshell which is slow absorption. Earth Juice Mircoblast, which is fast acting. (a must buy!! Has lots of 2ndary nutrients).
Now if you added to much chemical nutrients and or organics,( which is hard to burn your plants when using organics) You need to Flush the soil with plain water. You need to use 2 times as much water as the size of the pot, for example: If you have a 5 gallon pot and need to flush it, you need to use 10 gallons of water to rinse out the soil good enough to get rid of excessive nutrients.
To fix a calcium deficiency you can treat by foliar feeding with one teaspoon of dolomite lime or Garden lime per quart of water, Or Any Chemical/Organic nutrients that have Calcium in them will fix a Calcium deficiency. (Only mixing at ½ strength when using chemical nutrients or it will cause nutrient burn!)
Or you can take crushed up dolomite lime or garden lime in a gallon of water and water it in the soil. 1 to 2 teaspoons per gallon of water, which will be slow acting. Garden Gypsum, which is medium absorption. Limestone, which is medium absorption, Rock Phosphate and Animal wastes which are both medium/slow absorption. Note: Caution when using gypsum to an already acid soil (pH that is less than 5.5) can have a very bad effect on different types of plants by effecting the absorption of soil aluminum, which is poison to plant roots.

whatever you do better get on it. 5 weeks in that hurts....

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Let me take what you said Bloomin and make sure I get it right. I've locked out pretty much all the nutrients because I shocked them. My best plan would be to continue flushing with RO water and maintain my ph for a couple more days, little more than a week total. After that I should introduce a fraction of the nutrients back to the plants for the final week or so before I flush. In the end, at best, I can probably salvage my grow and pull some good smoke? 5 weeks in def hurts, but it's my first grow so ill chalk it up to a lesson learned. Thanks again for the help guys!