First Timer, What am I doing wrong?

no one can tell me what these spots are? as far as I can tell the brown spots are no longer spreading so whatever caused it is gone but for future reference id like to know what it is and how to prevent it. my guess is that since these spots showed after adding in calmag to my nutes that I over did it on the calcium which locked out other nutrients. i immediately stopped using the calmag and have not seen any further spots but the existing ones did get slightly darker. I may have just answered my own question but im so unsure of everything as this is my first time. the GDP which has more spots than either of the other two is also the greenest fastest growing out of the 3 strains with deadhead not far behind. oddly enough these are the two strains that have the spots and the bluedream has none.

The blue dream is still giving me problems though, the tips are turning a grayish brown with some tips curling up and some curling down on the same plant the tips are very brittle. PH is 5.8 in and runnoff is 6.1-6.2 but have researched repeatedly that the runoff PH doesn't mean a whole lot with coco. ppms are about 300 going in (this includes tap at 150ppm) and ~270 coming out

Well I have what I have and will use it. Thinking about something different for the clones I intend to put into flower and use the DG for the mothers. the GDP and the Deadhead are showing so much improvement that I don't really think its the nutes but I did a ppm test and they do seem very concentrated about 100ppm per gallon at 1ml/gallon of the grow protekt is about 10ppm per gallon at the same ratio and calmag came in at 45ppm per gallon. Stopped using calmag as i have a lot of calcium in my tap and it was overkill. mag try some epson salt though. When i checked them today all of them are rooting nicely in that I can see roots along the sides of the pot when i squeeze a side open. will be transplanting to 10x10 pots soon.

currently giving the GDP and Deadhead 300ppm and the blue dream half of that because it just doesn't have the roots yet that the others do. all the new foliage is looking great and as long as it stays that way then I say problem solved. will post some pics in a bit.

As far as PH the DG foliage pro does bring my 8.1 down easily but the protekt adds PH like crazy. I wonder if its really needed.