Ca problem?

[BII]

I spoke to the owner of one of the local hydro shops and he was certain that it looked like rust fungus not deficiency. I don't know if I agree with him though, I don't see anything that looks like spores on the underside of the leaf and nothing rubs off when I rub them. Anyone here have experience with rust fungus? I don't want to spray my flowering plants if I don't absolutely need to

Unless you have high humidity and/or poor tent ventilation, fungus/mold spreading like that should not be a problem.

Have you looked at the spots under a microscope or magnifying glass? Fungi would likely appear more as a growth on the leaf, while nutrient-related spotting would affect just the leaf tissue and not extend above the leaf surface.

 

[jER]

My humidity has been relatively stable at around 40-45% and I've had my 6" exhaust fan running 24-7.
I had a look with a microscope and the spots didn't look raised at all, if anything they were sunk in a little. Also the spots seem to start on the top of the leaf and work their way through to the bottom (some were visible only on the top). Everything I have managed to find on rust agrees with you @BII that it should have 3d bumps on the underside of the leaves where the spores form. I don't think this is rust at all, good thing I didn't follow the stores advice and spray fungicide all over my buds!

I did find another possible cause for the spotting problem, I had started a new set of bottles of base nutrients just before I left, and yesterday when I was mixing a fresh 80L tank I noticed that the Micro looked a lot darker than I remember it being in the past. I went out and got myself a brand new bottle of micro to compare and there was a definate difference between them:

The new bottle had a nice reddish colour and was fairly translucent where as the origional bottle was super dark brown and completely opaque.
I am pretty sure this is why I have been having problems with airstones plugging up super fast as well.
I ended up having to dump my 80L tank I had just prepared and start over with the new micro and the difference is clear. My tank is a black 100L tote and I have 1/4" white tape lines on the inside of the tank every 10L. With the origional micro 120ml in 80L of water I couldn't see the white line down past 30L at all, with the new micro I can see all the way to the bottom of the tank no problem.
AN nutrient grower support said its not a problem, haha like having airstones plug up completely the day after a rez change is completely normal! I am lucky I caught that when I did as I have to go back to texas again right away.

 

[BII]

Send AN your picture, tell them you are not satisfied with their degraded product, and hopefully they will send you a new 1 L or a discount coupon.

 

[jER]

Yeah the hydro store here swapped it for me, AN is pretty good about their money back guarantee. I don't think the $20 cost of a liter of nutes is significant compared to the loss of yield from stunted or failed crops though.