FWIW I have never PH'd my water.
FWIW <---- ??
pH is important, but as long as its in the general range, its not a big deal. i havent checked my pH in years. just knowing the water outa the tap is close to 7, and my nutrient teas dont usually end up outside the 6.5-7.5 range is fine. the important thing is the soil, good soil will be slightly acidic, and adding in the proper amount of nutrients wont alter it too much.
either way, the eye dropper bottle for fish tanks, from any pet store, 10 bucks.
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to the original post, its also the first set of leaves, they might just be dying cuz they are down and not getting much light? could be feeding it too early as well, i dont feed mine til they are well over 1ft tall. could have been a pH issue, or some odd variation of some nutrient, i wouldnt worry too much tho, overall the canopies look fine, as long as you see growth, your good.