I just read your diary and what I suspect is a minor PH fluctuation from your spike to 6.7 and you changing your water to 5.8 to bring it back down..Those rust marks and placement are typical of ph fluctuations and if you go and Google and compare you'll see for yourself that's likely what it is..Typically with Gaia which I'm running 100% right now with 4-4-4, 2-8-4 living soil and worm castings there are very little issues if any if you have a good microbial base and you might have just shocked them with the 5.8 watering...They look super healthy otherwise and I would wait to see now that you have the PH where you want it and see if this persist but I don't think it will at all....Good luck nice work...