leaves have brown spots/holes

i have just been to check on my plants and have noticed that on a couple of the lower leaves there seem to be some form of spots / holes, does anybody have any idea as to what this might be, i have had a look at plant problem guide, but it does't seem to be on there.

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My vote would go to it being a calcium deficiency. Do you use RO or bottled water? What nutrients are you using/amounts? pH? Do you have an ozone generator?

Picture of calcium deficiency:
View attachment 1200237

Add 1 tsp of Cal-Mag per gallon of water. If you already use it, adjust your PH.

Hi everyone I have the same problems also, where can you get cal-mag from and is that the name of it? can you get it from k-mart home depot?

Cal-Mag is made by Botanicare. Ordering online is probably your best bet if you don't have a good gardening or hydroponics store around. But you should be sure to check your soil or reservoir pH as that is often a cause of Calcium deficiency (there might be enough present but the plant simply can't uptake it) and can lead to other nutrient problems as well.

"My vote would go to it being a calcium deficiency. Do you use RO or bottled water? What nutrients are you using/amounts? pH? Do you have an ozone generator?"
erm, i use tap water, i am using canna coco a and b plus canna pk13/14, (8ml a and 8ml b plus 3.5ml pk13/14 per 2 ltrs of water) i do not have an ozone generator, dont even know what that is. my ph is around 5.5 is that good bad what?

Just to maybe help you research some, potassium competes with calcium and magnesium (check and possibly lower the amount of PK 13/14?). Coco coir is sometimes known to cause issues with plants absorbing calcium (ensure coir is buffered well before use and supplement with calcium if needed?).

A pH of 5.5 would be within the ballpark recommended range for hydroponics and within range for calcium uptake so I wouldn't mess around with the pH personally.

And wanted to add, many people use epsom salt to supplement calcium and magnesium, but I haven't ever used it personally. There are posts regarding how to mix and add it on here if you look around some.