We are on septic and when the shower is used the toilets gurgle and bubble we have put a root kill tablet in and also a drain kill solution but it is still happening how do we stop the septic symphony

One of two things are happening here.
1) There's a blockage (roots?) between the house and the septic tank. **OR**
2) Your drainfield is so loaded up with water it can't accept any more liquid so the septic tank fills up up and can't disperse the liquid the house puts into it.
The bubbles you see are sewer gas bounced back when the discharge hit the blockage.

If you can locate the house clean out open it up and flush a toilet, If the water backs up you have a septic system problem.
If that's the case it's time to call in the pros. Good luck, Tom