Too many factors, no one will be able to accurately answer and pin point the problem. Cubase is like a tape machine except more accurate, what you put into it is what you get. The issues you are having are all related to sound engineering. Technology and gear will never be able to replace the skills of a sound engineer. This is why many people recording at home still go to recording studios to have their songs mixed by a professional engineer. This is also why many of the large studios are shutting down. Because talented engineers are operating smaller studios and turning out better material with less gear and less overheads and can therefore charge less. If you were to go into a good local recording studio and watch what they do and how they were to process your files, you would have a better idea of what you need to learn. There is a good possibility that the mics were out of phase if you used 3 mics, two of the same mic is enough to start with. Different brand and model mics can have the opposite phase to each other and can cause issues even if placed next to each other, one might need to be phase flipped if mixing and matching different brands and models and/or they were not measured in proper distance from the source and again are out of phase. Or they might just need some good EQ.
Just out of curiosity, did you use the same take for each mic in each edit/cut by using Cubase’s group editing? You can google that, plus google mic placement and then look up on some sound engineering forums but you will learn the most by going into an actual studio and paying the engineer for a lesson.
These are the things I can think of that could be wrong
- Out of phase by mic positioning or by mic type
- Out of phase by not using group editing in Cubase
- Crappy mics in a room with bad acoustics
- Not EQed correctly
To see if something is out of phase, solo a channel of one of the mics, solo a channel of another one of the mics. Did the volume not increase enough? If there a phaser/flanger type of sound? Does moving a channel up just turn the other one down? Try panning them hard left and hard right. Does turning up one side turn down the other side? If you get a yes to any of those, there were recording out of phase. Best just to re-record it. You can try phase flipping one of the channels of shifting the audio of one of one of the channels left or right but doing so will probably break group editing so it’s best just to re-record in that case. If that’s not the case, then it’s either issues 3 and 4.