Rust spots on top leaves- one plant is much too yellow

Manganese for sure with the spots. A deficiency is rare and usually caused by high pH or excess iron. Manganese helps the plant to use nitrogen and iron for chlorophyll production as well as aiding in oxygen reduction. An early sign of deficiency is yellowing between leaf veins in new growth. This is followed by necrotic or dead spots on leaves. As it progresses, it will gradually spread to older growth. The most obvious sign is when the leaf veins and margins remain green around the yellowing of interveinal areas. It maY be deficient in MN but the lockout may be because of excess iron unless you have feeding something with iron in it. It's one thing to supply MN to the roots and hope, Manganese uptake almost triples at 5.5ph, but at 6+ its uptake is at minimal. Hot water has a much more acidic PH than cold, room temp h20 is roughly 7ph, boiling h20 is 6.1ph and once temp goes back to cold it goes back to 7. As there are two primary causes of a manganese deficiency in cannabis plants, fixing the problem is easier if you: Ensure optimal soil pH levels Prune your cannabis plants Use foliar feeding (Uptake through roots hindered) Apply nutrient It takes time to see results. The correction process may take six days to several weeks, depending on the weather and severity of the deficiency. As your plants recover, you’ll notice fewer leaves yellowing and a reduction in brown spots spreading to other parts. The tissue along the veins of some foliage may turn green, then merge and expand into healthy vegetation. Expect to lose those that are badly damaged. Monitor and adjust pH levels The pH level of your grow medium can cause a manganese deficiency in your weed plants. Besides following a cannabis feeding schedule, checking your soil helps detect conditions that may lead to a lack of Mn. Some lab tests can assess the nutrient concentration in your cannabis crops. Use the following guide to find the best pH for manganese absorption at the roots: Soil: 6.0–7.0 pH; lower it to 6.0–6.5 if you suspect your plant isn’t getting enough Mn. Hydro: 5.5–6.0 pH; crops absorb manganese when the reading is below 6.0. The manganese deficiency marijuana growers notice usually occurs when the growing medium pH exceeds 6.5. At that acidity level, cannabis plants can’t absorb the trace mineral. To remedy the situation, flush your soil with 6.0 pH water to remove excess nutrients and iron, which locks manganese out. Then, add a 6.0 pH nute solution that contains Mn to restore the level and help your plants recover. Monitor your watering and feeding to prevent the problem from recurring. Using high-quality fertilizers for cannabis crops and cultivation mediums offers the best protection against many ailments. Some nutrient lines can self-adjust to the optimal substrate pH level, making them convenient. There’s no need to use devices to check the condition. Prune your cannabis plant To solve a cannabis manganese deficiency issue, prune and dispose of leaves with symptoms to prevent pathogens and disease. It’s a form of defoliation. Don’t remove all the foliage at once. We suggest doing it in stages to avoid placing your plants under extreme stress. Use a sharp pruner or knife to avoid damaging the cannabis leaf when cutting it. Ensure that you sterilize the tools and your workspace to prevent contamination. Clean the area afterward. Use foliar feeding A foliar feed solution with this trace mineral helps to alleviate the manganese deficiency marijuana plants might experience. Most garden stores carry Mn sulfate, which is excellent for this purpose. Avoid applying chemical fertilizers at full strength as they may cause nutrient burn. Dilute them to about 50% and increase the dosage when necessary. Water your plants and the growing area thoroughly to improve the absorption rate. Spraying your crops corrects the issue faster than watering, as the leaves absorb more nutrients from the supplements. This method also delivers more carbohydrates into the root structure and prevents nute burn.