Did you add anything for the Water Kefir to eat other then the Coconut Water? (Glucose 50% Sucrose 35% Fructose 15%) This is the breakdown on the type of sugar in Coconut Water.
I've noticed a trend on enthusiast sites where sugar suggestions are heavily influenced by their mineral content. I mostly stick to cheaper pure sugars and use blackstrap molasses(sometimes sea salts) to provide minerals. If coconut water gives you good growth, I'd keep at it. You're going to need to supplement whatever sugar you use with an amino acid source. There are at least 3 known strains that can build the polysaccharide of the "grain", one of them consumes predominantly sucrose another predominately glucose and one can use either. Also, ph balance matters a lot (grain grow is best at ph between 6.5 and 5.5).
Lifestyle of Lactobacillus hordei
My guess is the type of kefir, need more sugar*, on the second fermentation it ran out of food. While I rarely use Coconut Water, I have had this happen to me before.
What I would do is feed the kefir grains, and focus on building up a good grain set, then start to train the grains to accept different types of sugars, and see what they do best. You can train them to use the different type of sugars but it does take a little while.
Justyn -'Doc'
