I would use
vmmanager to start/stop virtual machines. 15 bots is a good farm but you need to:
1) Create accounts one per several days. Accounts created on the same day easily flagged as a farm
2) Separate each account between virtual machines. Dont login to webside or game outside of vm.
3) Use IP from different subnetworks. Check for "route" in
ipinfo and try to find IPs with different routes.
Unfortunalely there is no garantee that your bots will not be flagged if you do
only one activity in game. I recommend to do other actions in game, like all you see in activity tracker. For bot farm it is impossible but you can switch activity once per 2 weeks (miner->courier->fw bot->repeat). Turn your farm to omega asap.