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This is the first time I've really adjusted water chemistry (other than adding some gypsum for IPA's). The krausen on this beer is the largest I've ever had. Would it be related to the water adjustments?

Could be.......but I assumed adjusting water chemistry had mostly to do with enzymatic activity during the mash and the flavor profiles?? Correct me if I'm wrong.

Yes. Probably.

Calcium/Magnesium/Zinc effect cell metabolism. If your water had an abundance of calcium, it could have been effecting yeast production. Now that you have done some water additions, everyone is "Happy, Happy, Happy".

FWIW, I always added calcium to my HFX and NG water profiles, as they are fairly soft.

I forgot to say, if your calcium content was high compared to the amount of magnesium and/or zinc it could have been effecting your fermentation. With the additions everything should be more balanced. John Palmer's Learn to brew talks about this topic a little bit (Chapter 6), something about if your calcium is too high compared to other minerals, you can end up with stuck fermentations or slow fermentations.

With some yeasts and fermentation temperatures I get a huge thick krausen that can last over a week. I just did an IPA with US-05 on the cool side (16C or so) that did that and have had it happen before with the same combination in other styles.