I'm guessing that the white stuff on the soil surface is salts, forming when water and fertilizer wick up to the surface and then the water evaporates, leaving salt behind.
If that's what it is, and not soil fungus, it's kind of bad for the roots. Salt (soluble minerals from fertilizer or from hard water") is bad for root hairs. Enough , can make it difficult for the plant to pull water out of the salty soil.
In general, it is desirable to create some flow right THROUGH the soil in the pot, from top to bottom so that salts can dissolve and be drawn out of the soil. The roots will etxract what the plant needs and leave the rest behind. That remainder needs to be flushed OUT so it does not accumulate in the soil.
Sometimes, water from the top until water comes out the bottom. Make sure you REMOVE that flushed water from the aluminum pan, or the soil will pull it back in along with aluminum ions dissolved into solution - also bad for roots.
If watering that heavily makes the soil water-logged, the soil is too "heavy" or "fine" - meaning that it retains too much water. In containers, the mix has to be "open" enough to let water drain out pretty freely. Then, there are open air spaces through which oxygen can diffuse into the mix where roots can "breath" it.
Roots need oxygen!
You probably don't want to re-pot any beans even if that was practical, so if the soil mix is too heavy, you have to aim for a balance of NOT over-watering TOO much (which would drown root hairs and eventually rot the whole root), and keeping the amount of salt build-up to a tolerable level.
A good start would be to prop the cups up on something to keep them out of any drained water. That will keep them from sucking excess salt back into the soil.
All this ASSUMES that the white stuff is crusty salt buildup.
If, instead, it is soil fungus, ignore what I've said.
