Hi mummy, hope your little one is feeling better soon! From what I've heard, NAN Optipro and S26 Gold are both popular choices here, but they suit different babies, some mums find S26 Gold gentler on the tummy, while others say NAN Optipro worked well for their babies with no issues. On the NAN Optipro vs NAN SUPREMEpro H.A. question, the key difference is that SUPREMEpro H.A. contains partially hydrolysed protein, which means it's easier to digest and may be a better option if your baby's tummy is still sensitive after the diarrhoea episode, my neighbour actually switched her baby to an H.A. formula after a similar situation and the doc said it was a good middle ground before going back to a standard formula. That said, every baby reacts differently, so it's really worth looping back with your doctor before deciding, especially since the diarrhoea is recent, they'll be able to advise which formula protein level suits your baby best right now.