Do I need Cal-Mag or what? Brown stains on the leaves.

And if your plant starting turn light green then she is hungry raise ec a bit if getting drake green than it has enough nutes.

You should use cal-mag for sure when growing in dwc , but i don't think that's the problem here , get the ph to 5.7-5.9. and add cal-mag a bit. Good luck buddy

I'm dealing with this in my recent hydroponic grows, the same symptoms you have show up in the same week as yours, you can check out my abandoned diary on my profile. I managed to revive that plant by increasing the fertilizer dosage and adding calmag. although it's not updated now. Many users told me it was a calmag deficiency, I found that adding calmag is never a bad idea and that calmag toxicity is hard to happen, from now on I always use calmag and it has improved. I also discovered that the ppm many recommend for an auto in hydroponics are not always the right ones, it's a matter of trial and error and chosen genetics. I would advise you to follow your manufacturer's feeding chart and reduce their dosage a bit and look for an intermediate ppm always below what your manufacturer recommends but in the same range. Right now I see in your diary that you're at 250ppm in the second week, I would recommend you slightly increase this, maybe to 350ppm. But the manufacturer's fertilizer guide will surely determine it better if you always go for a line lower. Your pH is probably fine at this stage at 5.6 but several experienced users recommended I go for 5.8, small fluctuations of 0.1 or 0.2 up or down shouldn't do anything, it's normal for that to happen, but lately, I've been aiming my autos at 5.8 throughout the vegetation and it's been working well. Another important thing, organic fertilizers are not recommended in DWC, it promotes the proliferation of bacteria and microorganisms in a very humid environment, many wouldn't advise using them although I know several do. I also saw you had problems with pH fluctuations in your diary, mineral fertilizers are more stable in maintaining the water's pH than organic ones generally, you would have fewer fluctuations if you use minerals instead of organics. I hope you can solve it soon, let me know the results via DM!

Hard to say, but I think it's root issues. Guessing the root booster your using is organic and being killed by the h202. Which might be the clear slime your getting. Roots should of dropped by now, only top feed every other to every third day and stop when the roots drop. A dry substrate can't harbour bad bacteria. As for food she shouldn't be showing any deficancies that young.