Is this a magnesium problem?

G.day. I have been having this problem over seneral crops and I have trried lots of things that my mayes tell me to do. now I need serious help so I'm asking if this is a magnesium problem, if so, how the hell do I fix? If not , can someone tell me what the problem is. The leaves start out with rust like spots then tinge on the edges and get rustier in colour, eventually they become dry and brittle as if they have been dried in the sun. I need help before I have to lose it all...again. please see my photos.

Have you tried Cal-Mag?
One teaspoon per gallon of water.
Mix with your other nutes every time .

No, whay is it? is it a calcium based product I don't think we have it in Oz

Cal-mag plus is made by Botanicare, it is a calcium, magnesium supplement. If you can't get it or don't want to spend the money you can just use Epsom salt, it is just magnesium sulfate. You can get that in Oz right?

With the purple leaf stems it could be a phosphorus deficiency. It could even be over fed causing nutrient lock out. It would show up as multiple deficiencies. What medium are you growing them in? Whats your PH/EC/PPM?

Scroll down to the Phosphorus deficiency pics, and have a look. http://www.icmag.com/ic/showthread.php?t=11688 Looks like it could be your problem, and looks alot like pic #5. I had that problem before and it turned out to be a PH problem(not PHing my fert mix), so it's hard to tell what could be causing yours. What are your PH readings and your feeding routines?

Yes we have Epsom salts, but still looking at which way I need to go, it is obviously a nutrient problem I have PH at 5.8 to 6 EC is 26 and growing in Coca I am using canna flores A & B, run to waste and water is reverse osmosis treated

I checked them again, the leaves are turning upwards and inwards, and I have flushed them with normal water, should I leave them for a day before treating?

I use milk of magnesia on my plants. It's magnesium hydroxide, it's way cheaper than the plant stuff u get online or at a garden store and like half the price(4.99) and u can get it in the pharmacy isles.