Originally Posted by gratus fermentatio
I'd freeze them solid & thaw them out twice. This will help to breakdown the cell walls & allow you to get more juice/flavour out of them. I'd also hit those berries with campden tabs. Regards, GF.
I'd also freeze them, then let them thaw. Then, I'd dissolve a campden tablet in 1/2 cup of water and pour that over the berries and let it sit overnight before adding them to my mead. I'd put them in the carboy, and then rack the mead into it.
The yeast you used is perfectly fine.