Got denied right off the bat from Discover. Rather disappointed. I called the recon line and tried to talk them into giving me an account but they said I have a collection showing on my transunion. My TU score is a 604. Took a hard pull for nothing. 
Sorry for the denial. Though Discover can be a YMMV on approvals/CL's. I don't think I've seen an approval with a CS in the low 600's. have you pulled your CR's? One Ca shouldn't hit your CS that hard? Have you been apping recently?
Rebulding pretty hard the past few months. I was hoping to graduate back to a big boy card. I had a $7200 limit Citi card that I was about maxed out on two years ago that I closed because I was offered a 0% interest repayment plan. I never should have done that. :/
Based on your siggy, I'd work on whatever baddies that are lingering on your CR's. if you have any cc's, keep your util down when you are going to app but more importantly- refrain from app'ng once you get your cs's to mortgage app requirements.