A double yolk sometimes happens, particularly with new layers or birds coming back into lay. It usually resolves as their systems get back in the swing of things. It's pretty uncommon for a bird to do it all the time. If that were the case, there isn't really anything you can do about it other than monitor and try to help if they have an issue. The double yolkers can be pretty large sometimes. The only other solution would be a hormonal implant to stop them laying completely, and those are not inexpensive and have to be redone periodically. It has to be done by a vet.
Blood streaks are not uncommon as well and can be from a very large egg, or if they strained a lot. It's usually a broken blood vessel, and generally doesn't cause any real issues.
Blood streaks are not uncommon as well and can be from a very large egg, or if they strained a lot. It's usually a broken blood vessel, and generally doesn't cause any real issues.