Some people have been known to have ovulation spotting, To cover your self make sure you keep bding for a few more days.
The last pic you took looked darker then the others so you could be just about to ovulate, some peoples lines don't get that dark though but still ovulate
so fingers crossed you catch that egg.
Mine is the same colour as yours at the mo, but according to fertility friend I am not due to ovulate for another 6 days but normally mine gets darker each day so I think I will ovulate on friday or even tomorrow... but dh has gone out tonight to watch football so will be in NO state to bd tonight