Coraline algae turning white?

[spawn]

Got home early today so I just tested everything. Not expecting to find much... & I didn't, but I did run out of the green liquid for the elos Mg test @ 15 drops, so I'll have to get another today & post later, although based on everything else I wouldn't expect to find much there either. Paras. are as follows
Sal. 1.026
Ca 450
Kh 8.5
Ph 8.2
No 5-10 on an Api kit it's been falling due to Vodka
All sps (27 of them) show signs of new growth & beautiful P.E. as I was away for a week. I would expect Mg to be 1300-1400 max. But there are only 2 small bits of coraline going white??