Spongy

First thing I would try is bleeding the brakes, you may have gotten a little air in the lines. While you are bleeding them, check for any leaks coming from the lines.

I would then check out the fluid level.

Tightening the adjuster may help. Make certain the wheel rotates 3/4-to-1 turn when you spin it. This is the proper drag on the drums. I would doubt that incorrectly adjusted brakes would cause a spongy brake pedal.

I have a question for you. Did you replace just the drum, or the shoes, wheel cylinder etc, as well? If you replaced the shoes, then you could have damaged the seal inside the wheel cylinder. If you replaced the wheel cylinder, you may have not tightened the brake line, or gotten a faulty cylinder.

Try these things and get back to me.