White/grey smoke during regen 2018 x15 cummins

The piece I showed earlier is under your cab between the turbo and particulate filter. You can remove it and look for cracks.

 

Mine will regen every 2 or 3 weeks

 

Stop and go, long idle or high idle time is the death of a DPF. It is probably time to have it cleaned or replaced. If the system is working properly, an occasional trace of smoke would be somewhat normal, noticeable smoke for a long time during the regen says the system needs service. Smoke can be from the system not reaching or maintaining the needed temp for a passive regen. Since you’re not seeing any fluid loss, it is not likely due to those being burned. Has it needed a parked regen lately? If not, maybe the service shop can do a computer forced regen. Forced regens can take quite a long time. Have seen some go almost 3 hours. While not an emergency, it does need to be dealt with. The possibility of taking out a sensor is high in this situation.