It mighty be root rot due to warm water which is a nice place for all kind of bacteria.
If seeds drop to the ground it usually is a good sign that the seed will / can germinate.
I never had a problem to germinate the seed between slightly wet paper towels in a dark place not more than 22 deg Celsius. I usually add old seeds to water for 24h to check which seeds went down and those will germinate pretty good.
If the brown root is not the tip then no worries, but if the acutal root tip becoming brown / mushy then it must be bacterial / rot problem.
I soak my seeds for 24-36 hours and then put in a wet paper towel, in a sealed Tupperware in a warm dark place. Typically I’ll put a cloth on my light driver which is outside of my tent, and place the Tupperware with seeds on top of cloth. Then I cover Tupperware with another cloth.
Never had a problem getting white taps to come out…
I cut RO (or distilled) water 2 to 1 with the 3% H2O2 (so it ends up as a 1% solution)
I use that for the bean soak and hydrating either the paper towel or the rapid rooter or the worm castings…
I’ve been doing the JPS worm casting method for a couple years now.
The H2O2 zaps any ‘lurking nasties’ and helps avoid damping off but is mild enough the seedling isn’t adversely affected.
Im with @Gpaw adding some H202 to your seed starting solution will really help.
I’m very fond of @JohnnyPotseed 's earth worm casting method as I’ve gotten almost 100% successrate since adapting it.
My method:
1: Stratify seeds in fridge for 24 hours.
2: Scuff the seeds in a sandpaper lined box.
3: Soak the seeds in water with a little H202 which kills the bacteria, aids in floating the seeds via microbubbles on the scuff sites, and softens the shell casing.
4: The soaking period is 12-36 hours in the dark at 24-25c.
5: When the tails show or at 36 hours I place the seeds into solocups prepared as follows: top 1/3 = Pure earthworm castings with the bottom 2/3rds = promix BX with earth worm castings mixed in.
The ewc was the gamechanger providing so much goodness for the developing seedling that so far the only times I’ve had failures is when the seed was dead to begin with.