I most likely have the same water as tiur mate in as well in it and in don't need cal mag, even know my water ppm is at a level they say you should use cal mag but I don't as it was giving me problems and since. topping 2 grows have been lush green good growth..
Their even a few articles saying
calmag is a load of shit its not needed for coco
I put money on it you need to stop
calmag completely to get the little ones to pull through..
Iv added
calmag again on bigger plants they grew fine look good, but when I then stop they look even better..
Also small plants just never once have liked it when in add it and pritty much do not grow for weeks and weeks