Faint line 2 days in a row

3 mornings ago I woke up and experienced some spotting, so I assumed my period was oncoming.

Yesterday evening I questioned if the spotting could have been implantation bleeding so I took the test and had a faint positive.

This morning I took another test and still had a faint positive. Should it not be a darker line since I used the first morning urine? There was only about 12 hours between the two tests, but I assumed the second test would be more pronounced since the pregnancy chemicals would be more concentrated.