Underpitched my yeast - should I pitch some more?

[HillWilly]

I pitched a single packet of Mangrove Jack's M07 on a 1.075 beer. The only instructions on the packet was to sprinkle on the wort, but it instructions on their web site states that you should pitch two packs for beers over 1.050, plus hydrate and stir for 15 minutes.

The beer has only been in the fermentor for 24 hours. Should I pitch another packet?

 

[JimRausch]

I have to say that you are getting pretty close to being too late.
In the 1st 24 hours, the yeast are multiplying like crazy, using up the O2, zinc, and other nutrients they need to get ready for the anaerobic fermentation that produces alcohol and CO2.
You may have stressed the yeast by asking them to do more than they were ready for, but most of the off-flavor compounds are already formed by 24 hours.
If you add more yeast after that, you are sticking them in a nutrient and O2 deficient environment, so they won't do much. You won't get much benefit.
If you do add yeast, they will need to be in an active phase- ie. from a starter at the high kraesen stage. So, I wouldn't bother at this point.
Good luck. Give the beer a good long(a week or so),warmish(upper 60's) cleanup phase after signs of primary fermentation are done, and you will decrease the amounts of off-flavors