Apfelwein with Grape Juice

I did a batch of 4 gallons apple, 1 gallon grape- dextrose, swapped out Moncharet for D47 wine yeast-

Expecting insane airlock activity 24 hours past the pitch- and I have gotta nothing but a few bubbles here and there.

I do have a few floating yeast colonies growing on top- much MUCH different looking as to when I did the regular apfelwein - 5 G apple, Moncharet yeast and dex of course.

Any reason for the slow start?

Its totally purple by the way- so I expect something interesting in the month that I take this thing into bottles.

Were there any preservatives in either juice?

None- 100% juice- no preserve- remember im using 4 G apple 1 G grape black cherry / concord grape blend- no preserve. 1 pack D47 dry wine yeast.

Had this been a regular apfelwein- the airlock bubbles per second would be off the chart at this point. But ATM we dont even have regular airlock activity- strange