Give Nutrients Too Soon – Giving nutrients too early will overload the seedling with nutrients – in a good soil potting mix, additional nutrients usually aren't needed for the first few weeks at least Give Too Much Nutrients At Once – Giving too much nutrients at once can cause a toxicity overnight – always start at half the recommended dose according to the nutrient schedule (most cannabis nutrients come with a nutrient schedule), and see how your plants react before upping the dose. Too much nutrients too soon caused this (tip burn) While the above seedling may look light colored, the problem is actually that it was given too high levels of nutrients. When there's too many nutrients, the plant can start getting light colored because some nutrients are getting locked out. The tip burn on the leaves is a good indicator that this problem is caused by too many nutrients.
Also this grower started with a "hot" (nutrient rich) soil mix, and there's no way a plant this size could have already used up all those nutrients. A lot of growers may think the way to fix this is add more nutrients since the plant leaves are pale, but that will actually make things worse! This plant just needs some plain water until it starts to use up the nutrients in the soil, and it will soon take on a healthy green appearance on new leaves. Nutrient deficiencies and other nutrient problems are most common when growers are using the wrong type of potting mix or cannabis nutrients. Two of the most common signs of nutrient deficiencies are pale or yellowing leaves and other unusual leaf discoloration . The most common type of deficiency is a nitrogen deficiency . The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft and sort of "fold" in, before turning crispy and falling off on their own. If the yellowing leaves are at the top of your plant or the yellow leaves are mosty new growth , then you probably don't have a nitrogen deficiency. Nitrogen deficiencies affect the oldest, lowest leaves first. There are many other nutrient deficiencies, and you can view them all here… Causes of Nutrient Deficiencies and Problems.
Soilless Medium w/o Hydro Nutrients – Some growers may start in a soilless medium and not realize it has no nutrients (with a soilless medium like vermiculite, coco coir, pertlie, rockwool, etc, it’s up to the grower to provide all the nutrients since they are inert mediums and don’t contain any nutrients on their own) which results in a deficiency if grower isn't providing extra nutrients. Soilless mediums are easy to grow in, but they do require the grower provide nutrients from the beginning. Don't Provide Nutrients As Plant Uses Up Soil – Many growers start in a good soil that has nutrients, but don’t give nutrients or transplant seedlings to a bigger container when the plant has started to use up the nutrients in the soil Wrong Type of Nutrients – Nutrient deficiencies commonly show up with the grower gives their plants the the wrong type of nutrients – generally it’s a good idea to give a “vegetative” nutrient formula for the first part of the plant’s life and a “bloom” nutrient formula for the flowering/budding stage. When giving the wrong time of nutrients at the wrong time, your plant won't grow as well. If you give vegetative nutrients in the flowering stage, you make it harder for the plant to form buds, while also increasing the chance of getting nutrient burn and other nutrient problems. Not Maintaining pH – If growers don’t manage pH, their plants may show signs of nutrient deficiencies even if the nutrients are actually there near the roots. Improper Watering Technique – Growers who don’t water properly (growing mediums stays wet or dry for too long, poor drainage, etc) often start getting nutrient deficiencies as the plant isn't able to effectively carry out normal plant processes Too Small Container – Nutrient problems crop up when plants are kept in a small container for too long without being transferred to a bigger pot (this is known as being "root bound" and can cause the plant to display nutrient deficiencies because the roots aren't functioning properly) Bugs – a lot of bugs and pests may initially look like a deficiency (spots on the leaves can appear from bites, or if bugs have infested the soil, etc) 4.) Heat – leaves bend in the middle so they look like canoes or tacos, turning up at the edges, wilting, strange spotting, symptoms usually appear after temperature starts climbing. When the heat gets too high, the edges of the leaves will begin to curl up and the leaves will begin to "cup" or "taco." Here's another cannabis seedling suffering from heat stress – notice how the edges are curling upwards. The solution to this problem is simply to lower the heat as experienced by the plant. Sometimes the leaves sort of fold downwards due to heat, too, like this seedling. After being subjected to overwatering plus a heat wave, the leaves of the following seedling started cuppping upwards and turned lime green. The stems and veins of the leaves were turning red. You can see the soil is still dark and wet because the plant stopped drinking after developing root problems. Cannabis plants often display heat stress when grown in hot, dry weather, especially when not given the right amount of water. Learn more about cannabis heat stress and how to fix it: https://www.growweedeasy.com/heat-light-stress. 5.) Not enough (or too much) light – burned or crinkled leaves, too much space between nodes, tall seedlings that fall over. Not Enough Light = Stretched, “Leggy,” Tall Seedlings. Stretched, “Leggy,” Tall Seedlings – Give More Light! This seedling is stretching too tall, with a lot of space in between sets of leaves, and a long thin stalk. This is caused by the plant not getting enough light. To fix too-tall seedlings, simply provide more light (usually by bringing grow lights closer or getting a brighter grow light) After giving enough light, growers can bury the extra stem, or just wait until the seedling grows out of it on its own. Burned, Crinkled Leaves – Reduce Light or Move Grow Lights Up. This cannabis seedling basically grew up into the grow light!
This cannabis seedling is being burned by too-close LED grow lights.
Answer: Moist but not drowning conditions, warmer temps, and a bit of light to help them start growing.