Yellow/brown spots?

Definitely a calcium deficiency. Acidic medium like 6.2 or below can easily lead to cal def. So will too much Potassium. If using coco that needs a little extra calcium. RO water obviously needs some added. Trace you steps, you know your routine better than anyone. They will also have a need for more calcium mid flower. Hope this helps narrow it down. Cheers 🍻

That can be a few things but main thing is its a root issue. First is too make sure not getting root rot. Proper drainage and o2. Medium should be loose not tightly compacted. If pass that go to the next possibly. Can be clorine from tap water. Make sure letting the water sit for 24hrs. Over dose of cal-mag - pull back from using. Iron/boron deficiency - add a rusty nail.

Hi, I am having the same problem with one of my plants. Maybe the plant might need more nitrogen, the ph is too high or low, and/or maybe it is sun light burn. Check on those first. Possible solution: 1. checked the ph soil. if it is to high or low, You have to bring you watering solution ph to 6.5. (Bring dow or up your water ph To 6.5 -7. Water the plants with the ph water a few times then check ph again.) Natural ph down: white vinegar Natural ph up: baking soda Or just buy a ph down or up solution. 2. Foliage feeding. Your plants used Some of their own nutrients to feed themselves. In a atomizer, add some of your nutrients solution, but used less of what they said on the label. Do a test run in one if your leaves before sunset. Wait a day. If the leave looks burn, then you used too much, if not continue the spray for a few days until the leaves get better. (Play with ratiosSee what works better) 3. Water time and where. Try watering before sunset or sunrise and not directly onto your leaves. Water drops work as a magnifying glass. Try watering your plants at their base and don't water leaves in the middle of the day. Don't water leaves when the grow light is on. Foliage spray before light goes off in your grow room. (This is from my own experience and some research. I still have not bring down the ph soil. It rained and I notice rain makes the ph go up) I hope this works for you and Happy grow

Looks like Calcium deficiency, but consider recent behaviour and check your labels of ferts and measure pH... eliminate other possibilities before adding stuff to substrate or reservoir.