DWC Brown spots - PH EC fine maybe Lockout?

You should give us the stats that all match, like E.C., pH, VPD, which fertilizer and how much, if you need a proper assessment. Could be a nutrient lockout. If you say it started in flowering, you probably changed the fertilizer and also increased it a bit, and that could be too much. Otherwise, it can't be much if you say pH, E.C., and everything is right :D But probably a combination of slight pH drift, too much or too little calmag, or the VPD just not being right, and the plant can hardly take up water. Did you notice anything with the water consumption? It should have increased a bit at the beginning of flowering and continue to rise. At least for me in DWC, that's how it is when everything goes smoothly, at least a liter. As mentioned here before, it can take a while for the problems to disappear. | Check again to be doubly and triply sure about the VPD; the pH 5.8 is what I always aim for, and it's best to do a reservoir change if you're unsure about the fertilizer and start with 2/3 strength. If you have very strong LED light and the plants are really stretching, definitely add extra calmag. Good luck!

I’d like to be able to connect this to a diary for more details on your setup and nutrient schedule. In DWC your PH needs to be between 5.8 and 6.2 to be the most effective. If it strays outside of this and remains high or low you’ll get symptoms like this within a couple of days. Check and correct your PH first before making any other changes. If not you’re guessing at what is wrong.

Calcium deficiency. These symptoms are from two weeks ago, it takes that long for deficiencies in the root zone to show in the leaves. It will take 2 weeks for the spots to stop once you increase the calcium, it will not happen in a day.

Overall concentration may be where you want it, but obviously there is an issue with nutritional balance if you have symptoms. So, it's not really 'fine' if you see symptoms Looks low on Ca or possibly high on P which could lock it out. Hihg p would also have light green new growth and maybe some more damage around margins (serated tips), so there should be visible signs to eliminate one or the other. in flower i'd shoot for PPM calculated from guaranteed analysis not a conversion from some cheap TDS probe. There is a big difference. One is gauranteed to be accurate and one is merely correlated. For flower phase N 80-100 P 40-60 K 180+ Ca 100+ Mg 75ish S 100+ This would be lwo end of feeding concentration.. if you fed well in vege, you often don't need as high of concentration going forward. For vege, i'd up the N to 120-130 ppm and everything else mostly stays the same. Your tap water may require a few adjustments, but otherwise the ratios of nutrients is good and overall concentration will depend on numerous local variables. This isn't 'my' formula. It's one that is used by several professional Ag fertilizer makers. it's a far superior formula to most marijuana brands. very few adjustments will be needed, and if they are they will be slow moving, easily identifiable symptoms with easy diagnosis and then never see again in future as you dial in formula. growbuddy? hydrobuddy? one of these free apps can take gauranteed analysis labels and tell you dose for target ppms. it's a very useful function.