@Hellhazard,My local grow-shop sold me some Hy-pro pH down. I just double checked the content and it is actually made of nitric acid. It should have been alright but since the first ph lock during week 5, the soils pH has been up and down for no reasons. Not fully controlling my climate (a tad too cold) surely didn't help also.
Thanks for the tips, next grow I'll buy a digital pH reader (much faster and easier to avoid pH fluctuations I suppose).
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