Coconut water kefir

Carnmore

Hi. I'm new to kefir making.

My first batch turned out well - fizzy and with a yeasty aroma. However, my second batch had a white coloured layer on top and was flat. I used the following ingredients:

660ml unsweetened coconut water ( 41g carbohydrate of which sugars per litre)
330ml filtered tap water
10g rapadura sugar

I left it to ferment for about 90 hours. I've strained this batch in to a fido jar for a second ferment. Two questions:

Why did this happen?
Will it be safe to drink?

The current batch is made up of:

660 ml coconut water and 30g rapider sugar - should that ferment correctly?

Thank you.