Since they are both rather near, 60 or 70 feet should be possible, in good circumstances, maybe it isn’t the signal strength of your router, in that area, rather a defective camera. Incorrectly soldered antenna, inside, for example.
A simple test, to make sure, would be to swap the cameras around. If the far one now works perfectly, whilst near, and the near one now behaves badly, whilst far, you know both cameras are equal, and unlikely to have any fault. At this point, the suggestion by Thomas will possibly solve your problem, but consider the ‘camera to sync module’ signal strength also. This needs to be good to both too, and will not be helped by a WiFi extender.
If however, the near one, when used far away, still works perfectly, and has more bars than did the camera it replaced, then you may have identified a faulty camera, and can report it to Blink for additional assistance in fault finding.
If swapping them around makes them work, you could also choose to live with the fact that one of them is better than the other for range, but continue to use the ‘bad’ one in a position that is near.
Simple test, soon done, and then you will know the best way forward.