Yeast question.

Here is my situation. I brewed 2 batches the past few days. My second batch has no activity 24 hours later. I know people will say give it time. I have NEVER had a batch take longer than 24 hour to be bubbling away. Both my batches used the same exact yeast. I noticed on my second batch the yeast pellets were darker in color, I would say a dark orange. The batch brewed the day prior was white with a yellow tint, both same exact yeast. I'm thinking it was a pack of dead yeast.
My main question is I have a spare pack of yeast. If I add it now. What should I expect if say the original pitch was OK and just dormant or something. Will I get a overpowering flavor or will it just speed up the ferm process and they will drop to bottom when there's no more sugar food for them?

Are they 5 gallon batches? The more I learn about yeast pitching amounts the more I learn its usually not enough. I always used one smack pack no starter in 5 gallon bactches. I shoulda been using 2. Pitch your extra yeast. Should be just fine, or better because they will have a bunch of dead brethren to feed on.

Don't sweat it, pitch more if your worried. ,it won't hurt.