I germinate my seeds by putting them in a washcloth saturated with bottled drinking water, then potting them. I am getting only 20 percent of my (seeds/sprouts) to flower in 3 weeks. I dig up the sprouts that did not sprout and I find they grow about 0.25 inch before turning black and dying.
Sounds like your seeds are staying too wet and the water could be packed with salt. I just checked a bottle of European water and found that it is packed with salts, sodium, calcium, magnesium, etc. That could be why they call it “mineral
water”! Sodium inhibits seed germination. When germination is arrested, the same amount of moisture is still given to seeds. When this moisture is not put to use by the seed, it creates unhealthy conditions for germination. The water lies on the seed or around it and causes rot.
You should have a germination rate of 80 percent or better. To solve your germination problem, change water. Use distilled water that has no other dissolved solids, such as sodium salt, to moisten seeds for germination. Set seeds in a moist paper towel. Prop the paper towel up so that is on edge (vertical) folded with the seeds inside. Keeping the paper towel vertical will make sure moisture stays at a safe level and drains away freely so that seeds will not get too wet.