Time to consider assessing Bee Health and Treatment Options. Great resources are on our website here.
Great talk by the NJ Apiarist on treatment options and testing: https://www.youtube.com/watch?v=OsG2QbUjsgA
Note that during the talk he holds up three distinct types of treatment
ApiVar Strips (Amitraz or Tacktic)
Mite Away Quick Strips/MAQS (formic acid pads)
A blue tub of ApiGuard (thymol)- also comes as ApiLifeVar wafers