*started typing this hours before duppiman's above post*
Tiffany is right on about chlorides in water, often amines are used these days too.
Letting water sit around only concentrates them!
I doubt very seriously that's the issue!
I've used my tap water for years, different plants, mediums and situations.
Even 2 different suppliers with no adverse effects.
Potted plants in a pot for years can build up mineral deposits, that's about the only thing I've encountered.
EVERYONE'S WATER DIFFERENT!
You can't rule that out.
You got alot of advice, basically all valid and correct, I'm just gunna ignore it and give mine too.
Growing EE indoors, out of season can be very risky!
For just the reason you've seen!
When their needs aren't fully met they slow way down growing, they can stop if things get bad enough, like winter!
At the point they are semi dormant, like yours are, then they can become rather susceptible to rot.
Heats the key, without enough then water becomes the enemy!
The roots rotting may be the plant going dormant, more likely they rotted because the soil stays wet!
Another problem is that the 2 you chose don't like the cold, and don't make huge bulbs, especially at that size!
Often dry dormant storing is best, but some types just won't have enough bulb at the size yours are at.
Without knowing the current status, I can't advise what to do, I can critique, and tell you I would have done...
Don't worry too much, if all else fails, and they don't make it, just contact me, I can load you up for pretty cheap next spring!
If everything is going well, don't do a thing!
We gotta find what works for each of us!
I'm afraid your mix is still not good, don't trash it, it'll be GREAT for summer time!
Theres a good chance it would even still work just fine, but I bet it needs more perlite.
What I plant in for winter time will be totally dry and crusty on top in 3 days, it will be ok down in there for a few weeks, kinna sounds like your mix is doing the same but I worry it's too moist...but I can't tell from here.
It's critical that the soil holds some moisture, but not much, for a decent amount of time.
I hate to admit it, but peat works great under the right conditions, I usually use lots of other stuff mixed in with it most times.
It's possible to even grow in pure peat, and feeding regularly.
The key is to mash and compress the peat down in the pot with your thumbs, if your mix if fluffy at all I always mash the mix in the pot, especially around the edge of the pot, it'll eat up alot of mix, or peat.
This will help the soil maintain the same moisture level throughout.
You don't want to be watering that often, but the soil cannot be dense or heavy, slick or slimey...it needs to be nice fluffy soilless mix, with lots of perlite or the like.
Lots of air, lots of drainage!
Let them go as long as you/they can stand.
If you can manage to get all that right then give them the most light indoors that you can, and the most heat, and that's all you can do.