I'm not familiar with that particular deck, but they all work about the same. I assume this was loud/amplified music? In that case, NEVER set the gain to "HIGH". You will always get distortion. Only use high gain for very quiet, unamplified music, or voice.
First question: Do you have a battery box? If not, stop reading this, go back to Sound Pros, and get the SPSB-10 or one of their other small boxes. You need to have a power supply for recording amplified music.
The general rule, taking it from there, is to plug the mics into the power supply, and plug that into the LINE-IN. If you can't get high enough levels with that, plug into the MIC input with "LOW" on. Only if you still can't get decent levels, go to MIC input "HIGH".
Turn all of the filters, level controls, and all that crap off. That stuff is not for recording music.
If you do all of this and you're still unhappy, then you are probably in the market for a mic upgrade
Virtually every person on this board unrepentantly fluffs the Church CA-11 and CA-14 small mics, and while I don't own a pair, it is true that nobody has a bad thing to say about them. Church also makes a small omni mic, the CAFS omni, that you might want to look into as well.