Turning Yellow

Potassium deficiency 100% take a look online and get yourself a chart of each cannabis deficiency. Learn the difference between mobile and immobile nutrients. Nitrogen phosphorus potassium and magnesium are all mobile nutrients. NPK are your macro nutrients and will be labeled first on every bottle or bag of nutrients you use. The secondary nutrients are calcium sulfur and magnesium, however only NPK and magnesium are mobile nutrients. You will see the deficiency occurring on the lowest oldest leaves. Knowing the difference that each one of these deficiencies will show will help you produce the best cannabis. Since the biggest nutrients NPK and magnesium are mobile you can kinda get an early warning for when your plant needs nutrients. The best cannabis is a hungry plant. So in order to achieve this you will want to begin feeding at only half strength and work your way up as the plant grows. So only feed your plant half, once a week. Until the first signs of a deficiency occurs. The plant will let you know what it needs and when. If your paying attention. Secondly do not over feed when flowering occurs. You will be dropping off nitrogen all together within the first two weeks and should only need no more than a 3% ratio at this time. At the beginning of flower you will need more phosphorus than anything else. Phosphorus helps the plant create bud sights and it does this by using the phosphorus to create a whole new set of root growth under the soil to feed the new bud sights. The plants stems themselves and buds are driven by potassium. However in early flower the best nutrient to use is potassium silicate. Blue planet makes gold shield potassium silicate. This will be your best and cheapest option since one bottle makes up to 80 gallons. The silica helps the plant create bud sights as well by giving the stems the strength they need to produce them. I use potassium silicate gold shield in my soil using one half teaspoon per gallon. Then a week or so before flower I will drop a half a teaspoon into a one liter spray bottle of spring water. I use this as a foliar spray. So once buds become full crowns of white hairs it's time drop nitrogen and feed less phosphorus and alot of potassium.

Nutrition burn. Autos are light feeders. Also pictures in white light make it way easier to see all issues. Good luck and happy growing 🌲🌲🌲👊

Looks like you're growing DWC/Hydro? Without further info on your parameters I can only guess this could be one of many things... Most likely your Ph and EC are off for this stage in the grow. For an auto flower you should be at 750-1050ppm, 1,7ec-2,2ec, ph 5.4-5.8. Also make sure that you are doing proper preventative maintenance on your lines, buckets etc. This would involve cleaning your setup in between reservoir changes. Most people do this with hydrogen peroxide.