Stumped!!

I need a bit of help here with a perplexing problem. I have two plants in a bubbler system suspended in a 60-liter tank in 2x 6-inch pots with a Hailea Aco 9810 silent air pump and two big airstones. Air temperature 70-73 degrees Fahrenheit Nutrient Temperature 67 - 70 degrees - Ph 5.8 - 6.2. I use the full range of Flairform nutrients apart from silica magic under a 600watt Light. One plant is a monster and looks like it's going to be a massive producer while the other looks to have a Calcium and Magnesium deficiency with rust spots on the leaves and is nearly half the size with slower growth but with the same healthy root mass. Now this is far from the first time I've grown in this system. The last time giving me over a pound of top quality bud. I change out the nutrient once a fortnight in veg and once a week in flower and I've never had this problem before.

In previous grows one plant has always been a bit smaller by up to maybe 20% and not giving quite as much in yield. I mainline and LST the plants to make the best use of the light and turn them daily. I've even swapped their positions in the tank to see if that would make any difference but to no avail.

Oh and I should say, the smaller of the two plants does not appear to be struggling in the sense that it is going from bad to worse, it's just not performing like it should, in my book but the strange thing is the Cal - Mag deficiency, if that's what it is?

Your thoughts.......................

Pic's will help,, use the search engine on here,, there's lots on how to solve your problem

I'm trying to get pics but can't get them off my phone onto my desktop to upload them for some strange reason. However, what you will see is rusty spots on leaves and only on one plant, I've already checked out the pictures.

Rust spots sound like calcium def. You can add 1/2 tsp gypsum to a gallon of water to get some Ca and sulfur into the soil. If you're entering flower you might have salt buildup (it's common if you haven't been watching your runoff ppms). If that's a concern, it might pay to flush with some gypsum water (say, 100% runoff).

az2000 said:

Rust spots sound like calcium def. You can add 1/2 tsp gypsum to a gallon of water to get some Ca and sulfur into the soil. If you're entering flower you might have salt buildup (it's common if you haven't been watching your runoff ppms). If that's a concern, it might pay to flush with some gypsum water (say, 100% runoff).

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It's a hydro bubbler DWC system. No run off just the tank changed out once a fortnight in veg and once a week in flower. I've never had this problem before and only with one plant.

Without pictures it's hard to say. But, calcium nitrate is the answer in hydro. Could be genetics. I get a plant or two with cal defs in soil when others don't.

az2000 said:

Without pictures it's hard to say. But, calcium nitrate is the answer in hydro. Could be genetics. I get a plant or two with cal defs in soil when others don't.

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You could be righ... I was thinking about a Cal Mag additive to see if it made any difference but for the moment I've refreshed the tank with a full complement of nutrients. The only thing I've changed is that now I use a humidifier because of the low humidity and it makes a difference when topping, the plants seem to recover quicker and have lush foliage, that is to say, larger leaves. I'm thinking about pulling the plug on the humidifier in the next few days and just letting them run into flower...