They only appear to work at first because you have caked on detergent residue in your machine. After that gets used up it's no better than using plain water.
Soap nuts are an option, they are a pod like shell from a tree that has saponifying plant chemicals in it. However, there is a quinoa-like problem with it, in that, like South Americans being priced out of their traditional food stuff as it becomes popular in the west, soapnuts are becoming inaccessible to Indians to wash their laundry with as they become popular with eco-conscious westerners.
Best thing, use a regular powder detergent, eco if possible, try a lower dose until you can notice a difference to efficacy. Or if your local health food/refill scoop and save store does it then buy from there to avoid packaging.
You could investigate the advanced hippy option and try native saponifying plants like soap wort or conkers.