My experience with CapOne secured( they only one I ever had), you may get a small increase after 5 months, but that depends on if you are in the credit steps program. Eventually, the Discover should unsecure from what I've read. If your scores are in the low 6's then you may be stuck for the moment where you are. You don't need another card to grow your scores, just as others have said use a lot of the limit, but pay off most of it before the statement cuts. Let one of them report a small balance each month. There is no reason to add another card and take that hit right now. Wait until your youngest card is over a year and then start thinking about another account.
Other than these actions, just do your time in credit purgatory and let your accounts age and work on removing any baddies you can. Over time your profile will improve and you will qualify for better cards. A lot of emphases is put on having 3 cards in this forum, but the only reason for that is the short term boost you can get from having an AZEO situation report. This is only a short term gain for that month and really does nothing for your long term credit profile.
