Have one plant where leaves have rusty spots and t...

I took a very good look at you earlier entries. This is my take on your problem, you've been having phantom problems that come and go most of your grow, even symptoms that I think you are not aware of: you have many leaves with the edges slightly curling upwards, which is a sign of heat stress. You've been careful with your pH levels, so it's not that. The rust spots you are seeing appear in the older / lower leaves so I don't think it's calcium deficiency, or it would appear on the newer leaves. The chlorosis is not interveinal, so I don't think it's mg deficiency either. I'm inclined to think it's potassium deficiency, because you have chlorosis with rust spots on mid lower leaves. But, your with your EC levels, I doubt you have any deficiency, if anything, it might be too high. Now, as I said earlier, you do have consistently signs of heat stress, this will make your plant drink more water than they would normally do and be forced to take more nutrients. Also, in veg you should not have to go higher than 1.0 EC for coco. What I believe is that you have a combination one or more of the following: heat stress, salt built up, nutrient lockout. I would do a thorough flush and dial back the feeding to no more than 1.0, and if the heat stress continues, even less. I would stop using so much liquid ferts too; use calmag and biogrow and / or fish mix, since they are both grow nutes (I would use Biogrow since it has more potassium) and rise the lights until those edges are no longer curled.

Looking back at you're entries i would say it's over watering, it really does help letting you're pots dry to get oxygen at roots which is critical for good development. If plant root's are in wet, oxygen poor soil it slows growth and stresses plant and can cause various symptoms. Most problems are often caused by environmental factors or growers over/under doing it, most quality nutrient's have everything required so deficiencies are fairly rare. This is a good source of info i use on a regular basis that might help you figure it out !! http://www.growweedeasy.com/how-often-water-marijuana Hope this helps mate, i've been there myself bro !!😉

All plants are differents... these spots are Cal deficiency , the EC in the growing medium is still too high for this lady