If you only had one bulb rot, I wouldn't worry about it. They are in the ground here and have survived for more than ten years. You have yours in a container where you have control over the drainage. I don't know what you used for your potting mix, but if you intend this for a number of years I would suggest you visit the container forum for suggested long lasting mix recipes. Al

I tend to think of L aestivum more as an honorary perennial than a typical bulb because it can stay in situ for years and form big tough permanent clumps which can be split up like perennials. They will not flower at the same time as your crocuses. Here they flower about a month after the crocuses.

I thought you were planting in the ground. If so, if you have areas where the drainage is of concern, such as the one with the rotten bulb, I just dig holes 3" deeper and line with 3 inches of rough gravel so that they drain really well. That has worked for me for all my bulbs for years.

Your snowflakes may flower this coming spring. However, they can take a while to settle in. As flora says, they are great for naturalising.

If I were to compose a planter and wanted crocuses I think I'd include something like Chionodoxa, and maybe miniature Narcissus, or one of the tougher fritillaries such as assyriaca because - both the snowflakes and the bluebells produce lots of juicy leaves which, when they are finishing, tend to smother whatever is under them. And they multiply faster than rabbits. Much. So other bulbs can be monstered.

One way around it is to plant up in separate pots and use the big container as a cache pot. When the little bulbs have done their run you can take out their pot and replace them with something else.

Bluebells do well in dappled light. Snowflakes are fine out in the open - even in pasture. Many crocuses prefer an open environment - good sun and fresh air, and good drainage, with very little in the way of competition from other plants' leaves.

Something else you might like, but could be too late for this year, are the small Irises - reticulata, etc, and Anemone blanda which gives a good show over a longish time.