Don't overthink Hi pass filtering, around 35-40 on kick and bass and 60-80 on guitars will be fine. The rest needs to be done with notches most likely. If you are boosting down there back if off some, but if you aren't then here's the plan: Solo your instruments to figure out where the looseness is, then (with nothing soloed) make an EQ point at around -3db and sweep it back and forth in the lows slowly until you find what sounds the best. Then bring the gain down further until it starts to sound bad, and back it off until it sounds good again. Do the same thing with the Q/bandwidth. Afterwards, if you feel you have to, do this on both kick and bass in the low mids (100-350) but at different frequency points and they will lock together a lot nicer. If the low end falls apart you are cutting too much or with too wide a Q/bandwidth. This method is very precise and should help you quite a bit.
And as always, use your ears, concentrate, don't get frustrated and you will get better at this quickly