The only product I use "late" in flower for mites is essential oils. I mentioned the wrong brand before, so I posted it above in this post. Notice the "organic" part? That means they use no pesticides, which would cause your product to fail testing when spraying this late.
As for not seeing any bugs in the flower room. I would be floored if you eradicated the flower room with the pesticides you used.
O yea, veg rooms should get sulfur. Becoming the industry standard for fighting mites.
As for predators, you have to call you bug guy and ask.
https://www.arbico-organics.com/category/beneficial-insects-predators-parasites is the company I use. He will put together a plan for releases, and what bugs should be used in your tent considering RH and temps.
For next year:
Beneficial bug release early
Sulfur sprays followed by beneficial bug releases.
Then before flower, hit them with a round of pesticides. I like
Grandevo, then
Venerate, then essential oils. This knocks down any possible populations.
After a couple days for the last rounds of sprays to mild out, then release more beneficial bugs.
Then one last time before flower.
That is my schedule at least. Mixed in with some stronger AG products.