Hey, bro,
I think you have two problems,
1, Over-Feeding, or nute burn. They are just not ready for a Big Mac Full Meal Deal.
2, Maybe some HEAT issues too.
What is the temp half way between the plants and the light?
Study this:
THE 8 STEP RECUPERATION AND RECOVERY REMEDY
1. Check the roots. If they are discolored, reddish or brown, or present an unpleasant odor, you have a problem. If they are weak, soft or mushy, you have a problem. Also while checking the roots, observe the temperature of the water. If it is warmer than "luke warm" you have a problem. This problem is probably what is referred to as "root rot" or a disease known as PYTHIUM. Remove the dead brown roots by trimming them away with sharp scissors. Do not leave them in the tank.
2. Check the humidity and temperature of the grow area below the lights in the "growing zone" when the lights are on. A temperature of above 87 degrees or below 67 degrees will slow growth, but it is not a serious problem that will kill your plants. Temperatures below 62 degrees or above 92 degrees will stop growth. An extremely high temperature in the upper 90s or below 58 degrees can slowly result in death of your plants. The most efficient temps for growth are between 72 to 84 degrees. Any Humidity between 40 and 60 percent is acceptable and desirable.
3. Check the "lights off, nighttime" temperature. Most desirable is ten to 15 degrees cooler than the daytime "lights on" temperature, averaging 66 to 72 degrees.
4. Check the distance between the tips of the plant and the tip of the light bulb. If you observe yellowing or leaf curling tips, then move the lights one inch further away. A good rule of thumb if you use HID lights, is hold the soft palm of your hand at the leaf tip and see if the bulb is too warm to your hand. If you use Stealth Hydro's compact fluorescent bulbs, we recommend a distance of three inches for the 65 and 85 watt bulbs and 4 inches to five inches for the 105 watt bulbs. More mature plants can handle the bulbs slightly closer.
5. Check the position of your fans. Air movement is very necessary for the health of your plants, but too strong of a fan can cause wind burn. Direct your fan toward the tops of the plants and toward the lights. Never position the fan blowing strongly downward on the leaves. If oyu have varible speeds, use the SLOW speed.
6. Add 2 teaspoons of hydrogen peroxide to a quart of water and add it to the tank of six gallons already in the tank. Wait ten minutes and then turn the water and nutrition solution pump off to prepare to drain the tank. Poor at least a cup of clean water through each grow cup, onto each rockwool cube and through the hydroton rocks.
7.Drain or pump the tank empty as possible without damaging the pump by running it dry. Add two gallons of additional clean water with 1 teaspoon of hydrogen peroxide again and then drain it away too. Again, empty the tank as empty as possible without burning up your pump.
8. Add fresh PH balanced water and nutritional packets as prescribed. PH test it again.
The above 8 steps should repair and remedy any health problems that your plants experienced within the next two days. Now is the time to try and determine what caused the problem to start with, by investigating and researching typical hydroponics problems and illnesses. Here are a few DIAGNOSIS TIPS.
Typical Hydroponics Problems and Illnesses
Underfeeding and Weak Nutrition
The entire plant, both upper and lower leaves, will show lime or light green in color.
The plant will not eat, drink or show growth.
It is time to follow the 8 Step Remedy.
Overfeeding, Use of Too Strong Nutrients
The leaves will curl downward. They grow very dark dull flat green and then the tips show signs of burn.
It is time to follow the 8 Step Remedy.
Nutritional Lockout
You know that you have made recent PH adjustments. You might know you may have used too much of the PH Adjustment Solution. You may have failed to test the PH often enough. You notice the plants did not eat or drink because they did not consume the same amount of water they used yesterday. You see rust spots. The large lower leaves are prematurely dying and you are not in the BLOOMING or FLOWERING stage.
It is time to follow the 8 Step Remedy.
Wind Burn
You had the fan blowing downward toward the upper side of the leaves, instead of blowing up through the node spaces or toward the lights. You observe the leaves becoming dry or even crispy, perhaps shriveling, and the tips curling upward. The leaves do not appear glossy, moist and vibrant.
It is time to follow the 8 Step Remedy.
Water, Nutrition Solution or Roots Are Discolored Brown Or Have an Unpleasant Odor
You notice your water is becoming brownish in color, or smells distasteful. Your solution does not smell pleasant and appetizing like fresh lettuce. Your roots are not the same shade of white that they once were a week ago.
It is time to follow the 8 Step Remedy.
