Flats often seem to come in groups, even when the cause is unrelated. Don't get upset, it's just part of cycling.

Sometimes there is a very small flake of stone or tiny piece of wire embedded in the tire. Just running your thumb around the inside won't find them. They only touch the tube when the tire is inflated and flexes as it rolls.

The best way I have found so far to find them is to remove the tire from the wheel and inspect the tread. Any cut or mark may be hiding an object. I pinch the tire to bend the casing and open up the cut or hole so I can look inside.

Also, cuts in the tread can allow the tube to get worn. As the tire rolls with your weight on it it flattens out. That spreads any cuts and lets the tube bulge through.

A rim strip which is bulging into the spoke holes a bit is ok as long as there are no sharp edges to wear on the tube.

It's always useful to note the orientation of the tube when you remove it, so you can inspect that area of the tire or rim. That's why I mount the tire so the label is aligned with the valve hole, and the colred side of the label is on the left side of the bike. That makes it easier to find the area on the tire where the flat happened.