Rust spots on leaves in flowering

Im in my 5th week of flower(white rhino)and my upper leaves are turning yellowish.Im running DWC.The root zone is nice and white.the temps and ph is good.Im only feeding about 700-900 ppm.Im using AN Connoisseur A B.And ive been running Big bud for a cpl weeks.the only leaves that seem to be affected is the upper leaves.Any ideas?

id say too much nutrients. leaves are very dark green ( nitrogen toxicity). i see no need to go past 700ppm. my plants burn if i feed them 900ppm. if your ph is on point you shouldn't have any deficiency. ive always know them rust spots to appear due to an issue with calcium.
are you running RO water or tap water

Im running RO.I just changed all the buckets and and adjusted ppm to about 600 ta 700 ppm.I raised the lights about a 1 1/2....I noticed on some of the lower leaves that arent totally yellow have some nute burn on the tips.So i think your right with to much nutes.do you think i should cut out the part A Bloom.i just read the bottle and its just nitrogen calcium and magnesium.

are you adding cal mag to your Ro water before adding anything else. if no id say thats the problem

inleague said:

Im running RO.I just changed all the buckets and and adjusted ppm to about 600 ta 700 ppm.I raised the lights about a 1 1/2....I noticed on some of the lower leaves that arent totally yellow have some nute burn on the tips.So i think your right with to much nutes.do you think i should cut out the part A Bloom.i just read the bottle and its just nitrogen calcium and magnesium.

Click to expand...

if its an A+B never exclude one always use both

Ya im not adding any cal mag to the water.there is supposed to be cal mag in the part A.Maybe ill buy a bottle of cal mag and see it that helps

inleague said:

Ya im not adding any cal mag to the water.there is supposed to be cal mag in the part A.Maybe ill buy a bottle of cal mag and see it that helps

Click to expand...

i dont use RO water but everyone says you must add 150ppm of cal mag to your RO water @ the start always regardless of your base nutrients having calcium and magnesium in it as it acts like a buffer. it helps keep your ph stable
i grow dwc using tap water so i dont add cal mag every feeding but any time i see rust spots or red stems ill add it to my rez
next grow maybe try using it or do some research on cal mag and reverse osmosis water. When using RO water for growing cannabis, it is important to use a Cal-Mag (Calciumand Magnesium) supplement alongside your regular cannabis nutrients. This is because you need to make up for some of the trace minerals that are normally found in regular water. many forms posts on here about the topic

Thanks for the help.Im definitely gonna grab some cal mag tomorrow!!!!

A few observations:

"only leaves that seem to be affected is the upper leaves"...along with the rusty spots, generally indicates a Ca issue. The leaves under the most direct light will generally be the ones to show.

I don't have experience running DWC, I'm a coco man, however I would tend to agree your plants are plenty green...to the point of toxicity; not in my opinion, but maybe more than they need to be...and too much N will cause you all kinds of issues with other elements. Ask me how I know.

For sure if you're using RO water (empty water), and your nutrient line doesn't give all of the necessary micros, Ca and Mg, included; you will have to add them. Keep in mind, Ca and Mg, may not be the only ones missing so be sure you're getting what you pay for in terms of what you're using as feed. Conversely, rather than buying the proverbial CalMag, see if you can get Calcium Nitrate and a bag of Epson Salt...this way, you can add Ca by itself and Mg by itself, rather than always tag teaming the plant, when in fact it may not want one or the other. There's no need to feed what they don't want.

*CaNi does impart Nitrogen so maybe this would be counter productive for you considering your feed; that's something you'd have to decide, but for sure it makes Ca readily available to your plant.

Good luck friend.