When I did a full washer full I found the toilet full of bubbles & low in water-help!
The well should not be low as we have had a long wet winter~~

A septic system only has a certain amount of air space in the drain lines and the tank. Suds take up a great deal of space and do not flow as easy as water. Maybe you are using a bit too much detergent and when the washer drains the suds over fill the air space. I do not think you have a plumbing issue like a clogged drain or failed septic. Try a different detergent or at least less of it.