I had the same you need to dose with potassium and iron with a syringe directly on the HC. Also pump up the CO2 by huge amounts you want drop checker to be yellow unless you have fish. Please don't if you have fish.
I have mine at 5bps...
See mine when doing dry start

Then submerged with some melting

And now - also tree growing back.
https://vimeo.com/199570685
And the pearling...

Plus colour of drop checking but I have no fish...

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