FICO Score question...

My DH and I are sooo upset. We were working on getting my DH FICO score back up a few points so we get approved for this loan that we need really bad. Well, we only needed to get it up 5 points, now I just checked his score, and it went down more than 20 points??? I don't understand... we paid more on each of his cards this past month and now it score went down instead of up? Nothing has changed on it, so I know that's not the reason why! The only thing I can think of is that my name is on one of his cards, so maybe my credit affected his score? Is this possible? All my other cards and his cards are in only our names. I'm listed as an additional card holder for this one card. If it does affect it, if he takes me off the card, will that help his score? We're so upset. It's going to take us so much longer now to get the score up. Please help!