Bud rot on plant in veg?

High humidity for a new grower is a death sentence until you get your HVAC on point with a solid negative pressure, Around Week 4 of the flower period? Just a guess. All fungi require moisture to some degree for survival and growth. It's high RH-related at its core. Either in the medium or in the air. Crippling movement of water, just enough over time. P uptakes with oxygen 6.5-7.0. PH most likely skewed. A possible combination of bad water circulation and a progression of skewing pH and exacerbating the uptake to boot. Calcium is generally taken up via transpirational osmosis. While it's often described as a passive process, occurring with the flow of water, it's more accurate to say it's facilitated by both passive and active mechanisms. But when it needs to switch to active transport, it uses energy/ATP to do so. The only way you can get fungal and bacterial infections is by giving moisture time to stagnate in pots. They suffer slowly from a lack of oxygen and/or a lack of water movement. The longer it sits without movement, the higher the chance of nasties. Transpiration is the daytime process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems, and flowers. It is a passive process ... transpiration is responsible for 90% of water loss in a medium during the day. Transpiration creates turgor pressure, which drives osmosis, which creates water cohesion and uptake. When oxygen uptake is low, ATP (adenosine triphosphate) production decreases. The primary pathway for ATP production in the presence of oxygen, oxidative phosphorylation, is impaired. This leads to a shift towards anaerobic pathways like glycolysis, which produces ATP less efficiently and can lead to a buildup of lactic acid. The buildup of lactic acid in a plant's medium, such as soil, can lead to a decrease in pH, potentially affecting microbial activity and nutrient availability. While low concentrations of lactic acid can promote plant growth and enhance nutrient uptake by stimulating microbial activity and potentially increasing the availability of micronutrients, higher concentrations can be detrimental, inhibiting plant growth and affecting the overall soil health. A lack of oxygen in soil, often occurring in waterlogged or compacted conditions, can lead to an increase in carbonic acid. This happens because when oxygen is scarce, soil microbes switch to anaerobic respiration, producing carbon dioxide (CO2) as a byproduct. This CO2 then reacts with water in the soil to form carbonic acid (H2CO3). Carbonic acid can be beneficial for soil in some contexts, particularly when used to manage pH and improve nutrient availability. It's a weak acid formed when carbon dioxide dissolves in water, and it can help lower the pH of alkaline soils, making nutrients more accessible to plants. Additionally, carbonic acid can stimulate microbial activity and improve soil structure by promoting the production of glomalin, a "soil glue" that aggregates soil particles. Do I have to worry about her? Probably. If the environment exists for it to occur on one plant, then it comes down to a matter of tolerance, possibly that the one plant that was affected first was in a dead spot for airflow compared to other plants, hard to say either way. Anytime you see black, black spots or a black, sooty coating on leaves it's often caused by fungal diseases. Fungal leaf spots can take a week or more to become visible after the initial infection, so by the time you get a visual cue, it's too late already. *Most bacteria multiply most rapidly at temperatures above 77°F (25°C), often referred to as the "danger zone". Within this range, bacteria can double their numbers every 20 minutes. Bacteria need nutrients, water, and a suitable temperature to grow. We can't control nutrients without disrupting plants' growth, we can't control temperatures without disrupting plants' growth, but you can control the water and how fast it cycles between two separate atmospheres, the air and the medium. Evapotranspiration (ET) is the process by which water moves from the medium to the atmosphere through the combined efforts of evaporation and transpiration. Evaporation is the direct change of liquid water to vapor from surfaces like soil and water bodies. Transpiration is the process by which plants release water vapor from their leaves. Remove the possibility of bacteria taking hold by creating an indoor environment that ensures no moisture will sit for long enough to stagnate and bacteria take hold. While drought stress is generally detrimental to plant growth, it can also induce some beneficial effects, primarily related to enhanced plant defense mechanisms and changes in resource allocation. These benefits are often associated with moderate drought stress and can include increased synthesis of beneficial compounds, improved drought tolerance, and potentially even enhanced nutrient uptake after the stress is relieved. When a plant wilts, it means it has reached a point where it's using more water than it can absorb, leading to a loss of turgor pressure in its cells. While it's difficult to say exactly how much water is left in reserve, the plant has likely used most of the readily available water in the soil and is relying on the water clinging to the soil particles. From my experience, you have droop around 10-15%, giving you 16-24 hours(given conditions) to water her back to life before any perma dmg is done, generally I wait until I physically see a droop.

If it has rot in the buds then the spores are in the air and can happen to the other one if they stay in there. cut out the rot, and spray shit down with some peroxide. If u can remove the other plant.

P deficiency (last stage ) OR something that cause its lockout check ur Ca ppm to be sure (if yellowing goes from top to bottom then that's it)

If u would have bud rott u should kill the main cola because its Toxic to smoke , but from ur lewves u have root problems from too much

Blueish color indicative of low P. Whether that is physically low P around roots or ph lockout or nute lockout is unclear. I don't think this is part of your bud rot.. you sure you have some rot going on? discoloration of buds, dead sugar leaves, maybe some fuzz under the buds? if so cut widely around it and dispose of it as carefully as possible while spreading as few spores as possible doing it. maybe wrap in plastic before cutting/agitating it. Once you can see such a thing, it's already capable of spreading wildly. you may think something looks clean but 2-3 months after harvest it'll feel like dry-rot - super soft. then you know you've been smoking mold-infested weed for 2-3 months, bwahha.

Where were the leaves on the plant from? This could be a few things. If it's at the top of plant and newer growth it could be Calcium deficiency. It could also be environmental stress. Make sure basics for growing conditions are all good, if not then adjust them. We can't always jump to nutrient issues if any of her environmental needs are wrong. Heat or light stress can cause this.