The
diatomaceous earth will probably be fine for the soil. But you are going to need to treat the plants too. I wouldn't do anything to the plants in flower. You never want to put anything on your buds. But when they're finished flowering, before you put the others into flower, i would try treating with either
Sierra Natural Science, Safer Soap, and or
Neem Oil. You can rotate every 3-4 days to try and break their growth cycle. Remove plants and heavily disinfect rooms/tents with a mild soap and water solution with a small amount of bleach. I spray the tents with Safers Soap and then wipe them all down, then use like some clorox wipes or a mild bleach solution.
At the same time spray all vegetative plants, being sure to get the tops and bottoms of leaves. I also spray the soil surface and the drainage holes at the bottom. Just in case. Do not spray them while they are under your grow lights! They will burn! I usually remove them out of the tent, and even trim and remove alot of the big fan leaves. Less places for them to hide. Then give them a good soaking. Sometimes twice in a day, while simultaneously cleaning the tent, fan, and any surfaces around my grow. Once the plants are completely dry, only then do i put them back under the grow lights for a few more days and then repeat the process. I would try to do this at least 4 times. Maybe 5 at 3 to 4 day intervals. Then once a week after that for a regular IPM schedule and to prevent anything from coming back!
All the while checking and inspecting plants and undersides of leaves for any new damage or any new critters.
If a few weeks or more go by and no bugs, try another flower run.
Good luck to you.