Mine has turned from green to yellow.When you say it crashes, what does it look like? clear, non-opaque?
Also looking at some pics of the four strains in ocean magik, two of them are bright green (nannochloropsis and tetraselmis) and two of them are yellowish brown (isochrysis and thalassiosira). My concoction is somewhere in between, so I'm hoping that I have live phyto that is still some mixture of the strains, and it will go one way or the other as I continue to split and one strain dominates. But then again...I could be growing some toxic bacteria instead.
If you wait more, the yellow pretty much settles at the bottom and you're left with clear water with nasty stuff on the bottom.
In my cases it has turned from nice green to yellow in half a day or so.