Its not nute burn although youd think it was with the cocktail of stuff you have in the mix. Next time start the seedlings in lighter mix like coco or peat until you get your medium and feed dialed in properly. You cant just throw a random mix together and expect it to work like a pro grower .
Anyway here is some info on nute burn.
Nutrient Burn
by Nebula Haze
Is it Nutrient Burn?
Also commonly known as cannabis "Nute Burn"
Quick Summary: Nutrient burn is one of the most common beginner cannabis growing problems, and is a result of the roots taking in more nutrients than a cannabis plant can use.
This excess level of nutrients causes a brown or yellow "burn" along the tips of your leaves. If nutrient levels are not lowered, the burnt tips start traveling inwards and tend to get crispy and twisted.
Take me straight to the solution for nute burn!
Nutrient burn is most common when feeding cannabis too-high levels of
bottled nutrients and especially chemical nutrients (for example - hydroponic setups often use chemical nutrients that are easily available to plant roots because they increase potency and yields, but these nutrients are so accessible to the plant roots that they can cause nutrient burn if the grower adds too much).
Nutrient burn can also happen when plants or seedlings are grown directly in soil that has a high level of nutrients (a "hot" soil or growing medium) such as fresh compost, manure or a nutrient-amended soil mix. This usually happens to young seedlings, and they will "grow out of it" as they begin to use up all the nutrients in the soil, as long as more nutrients are not added.
Problem: You will notice the tips of your leaves showing the first signs of nutrient burn by turning yellow, tan, gold or brown. A light case of nutrient burn will only affect the tips of your leaves.
The yellow tips will eventually turn rusty brown and crispy. If you do not correct the problem, you may also notice the burn slowly spreading from the tips to the whole leaf. At this point, if you haven't done so already, you should immediately treat your plant (directions below) before there's more damage.
Nutrient burn can also manifest itself as brown or bronze spotting around the edges of the leaf serrations (often when there's an problem with proper absorption of potassium), or with leaf tips curling downwards (tips pointing down is often associated with too much nitrogen).
Nutrient burn can cause burnt spots on the serrated edges - not just the tips
(often caused by the plant absorbing too much potassium)
No matter which kind of nute burn you have, the solution remains the same (full instructions below)
Why Growers Should Care About Stopping Nutrient Burn
I have heard some growers say that a little nutrient burn is actually a good thing, because it means that you are giving your plant the highest level of nutrients it can use. A lot of growers have the mistaken idea that nutrients are somehow "food" for your cannabis plants, and so more food = more energy = bigger yields.
This is wrong, instead
nutrients are more like a multi-vitamin for your plant. Just like you can't give a child 10 multivitamins a day to make them grow faster, you can't give your plants 10x the regular does of nutrients and exact anything good to happen.
The real "food" for your plant is
light. Your plant produces energy from light through a process known as photosynthesis, which is most effective when the plant has healthy green leaves.
Your leaves are like solar panels, and the energy produced by the leaves is used as energy for the whole plant. You need the leaves to be in tip-top shape to get the most energy from the lights, so your plant has plenty of energy to grow and produce buds.
Therefore,
the biggest problem with nutrient burn is the fact that you are losing leaf mass and overall leaf robustness on your cannabis plant.
A little nute burn won't slow down your plants much, if at all, but if nute burn is left out of control, you will begin to lose serious leaf mass and it will dramatically slow down plant growth and reduce your overall yields.
What's worse, if excess nutrients are not flushed out of the plant's system before harvest, the buds may contain trace amounts of extra nutrients, giving the buds an unpleasant chemical-like taste. Speaking of the flowering stage... (
Wait, what's the flowering stage?)
Nutrient Burn is More Serious in the Flowering Stage
Cannabis plants spend the beginning part of their life in the
vegetative stage. When cannabis plants enter the second part of their life, the
flowering stage, they stop focusing on making leaves and stems, and put all their focus on making buds/flowers.
The flowering stage is the most vulnerable stage for cannabis plants, because they don't have much ability to bounce back from any problems.
The further you get into the flowering stage (and the closer you get the harvest), the less likely the plant will replace a leaf that is damaged or dies. By the time harvest is around the corner, your plant basically stops making any effort to recover from leaf damage, and it's complete focus is on fattening buds.
That's why budding cannabis plants need extra care to thrive - in the flowering stage, a
little bit of nutrient burn will probably be okay, but too much nutrient burn can seriously hurt yields because the plant will not be able to recover. If you are adding nutrients to your water, it can be very easy to burn your plants in the flowering stage (even with nutrient levels it was fine with before) as different strains have different needs throughout budding.
