Aw, first time mom moments talaga na nakakapag-alala, pero okay lang yan, nakita mo na ng pedia niya so you're doing everything right na! Seedy poop sa formula babies is actually common, especially during transitions, pero since may antibiotic at zinc na siya ngayon, give it a few more days pa to settle kasi the poop usually takes time to normalize after meds. For the rash, a few of us moms swear by diaper cream, I use plain zinc oxide or lanolin talaga, and make sure to let her air dry a bit after diaper changes para less moisture. But if the seedy poop doesn't improve in the next week or the rash gets worse, worth checking back with her pedia na lang para peace of mind mo, kaya mo yan!