That could be an issue that means lots of soil and very little water! Guess it could just mean plenty of room for roots not always being wet and some always in the moisture zone! Earthbox works so well cuz they have large reservoirs so when water isn’t full plenty of room for the roots to get lots of oxygen! Having a really low level reservoir kinda prevents that from being possible!
Also u may be able to just put the MC in reservoir! I’d just (if u don’t already) use a small cup of warm water to make sure powder fully dissolves and then should have no problem in reservoir! It’s mainly organic nutrients or a multipart system that can fall outta suspension as they sit! A reservoir that small water isn’t just sitting for extended periods!