That looks more like magnesium or salt build up to me but I could be wrong... calcium usually is crunchy leaf edges... but right about where you are in flower is roughly the point in a plants life cycle where it needs the most calcium and magnesium... also once those spots or damage happens, they will not go away even if you correct the deficiencies...
What nutrient line are you using and in what order are you mixing the nutrients?
If you use a silica product, that needs to get mixed first... then your base/main nutrients, then any additives, and then your cal/mag very last.. if you are NOT using a silica product; the cal/mag goes first and thoroughly... (note ppm) then your base/main nutes, then your additives... but the cal/mag has to go first in that case... in some cases/manufacturers things need to be mixed in different order or it doesn't matter; but in most cases those 2 ways are in which the way you should be mixing them... if you have any doubts, you should contact the manufacturers of the base/main nutrients you're using.... basically in a nutshell most times... if no silica, cal/mag is always first... if silica is being used; thats always first and cal/mag is very last... some nutes it doesn't matter how you mix them but 99% of the time it does matter, but as I said if there's any doubts; contact your base nute company and ask them; make sure to tell them what brand etc of other products your using...
In the end, what you're going to have to do is next go round, you have to add more cal/mag around that point in time... usually after the stretch and they start budsetting is when they'll require more cal/mag... if/when you resolve the calcium issue and you still end up needing more magnesium, you can buy Epsom salts from any pharmacy for like $6-7 a bag and be able to add mag without the calcium... but don't always follow the bottles recommendations... in most cases it's not enough with cal/mag for flowering, yet more than enough for veg... but usually their recommendations are way too much with base nutes...
I was following the manufacturers instructions from day 1 and was running a 3.0 ec until I realized most times you don't need much more than a 2.0 ec ever... some strains do but each strain has its own needs; that's how and why most times you need to grow a strain a couple times before you can really grow a plant to perfection... it requires note taking all the way through...
I was running blue planet nutes 3 part and when I ran low I'd use GH's 3 part which I'm using now but I converted to the Lucas formula for now as it's simple and cheaper for certain... But even though I have more years experience than I can remember in organic dirt; it means nothing in hydro other than I understand plants well; but I had to simplify my nutrient regiment because I was way over doing it with the 3 part base, silica, cal mag, bloom boosters... I chopped it to the Lucas formula and calmag... I'm literally using half or less nutrients than I was with better results.. it doesn't get any easier than Lucas 2:1 bloom/micro formula... it's old and outdated but it works very simply and is easy to figure out if you're doing something wrong or right... perfect for hydro newbs like myself...
But post up what products and how your using them, but my suggestion would be that you need to use either more cal/mag or figure out if it's either a cal or mag def specifically and take it from there... I'm a little worn out; and could have the deficiencies reversed but I thought spots were mag and crunchy edges was calcium... double check that one; but recommendations from manufacturers are exactly that...recommendations; each strain has its own requirements and needs at certain points of its life cycle; it's your job to figure out when they need what... and that's harder in hydro than soil (organic water only soil anyhow)... if/when I had a deficiency in soil; I'd just top dress with some worm castings or more of my soil mix... but usually I'd go from beginning to end with only water and some molasses here and there to give the microbial life a little blast and from there they and the plant work out who needs what... organic soil seems very hard from a beginners stand point but once you have it figured out; its simple... as is hydro once u know exactly what each strain needs but it's a bit harder to tune for each strain... there's very few all purpose formulas that will work perfectly for all strains... the Lucas formula is close but still requires tuning for each strain yet minimal...
hey all like the title says this is my first run at dwc. I'm about 41/2 seeking into flower. So far it's blowing soil away, But I've hit a road block and I can't seem to shake this deficiency. I believe it to calcium. I'm adding the appropriate amounts of calmag every time I top the Rez and every time I change everything out. My ph is right around 5.7-6.0 Rez temps are right around 60. My ppm is around 1100 as of 15 minutes ago.