Dusting with powdered sugar can help, the count in the larger hive isn't critical but if you're worried go for it.
The smaller hive actually has a larger Varroa infestation than the larger hive on a proportional basis. That one I would definitely treat.
Hopguard, is a new commercial Varroa treatment made from the hop plant (
) and seems to be effective and organic based. I have a hops plant growing on my bee yard fence and just drop a few hops into each this time of year.