Hello I feel your pain! It's horrible for then when a rash takes hold.
I use little lamb bamboo with fleece liners. They really help to keep DS's bits an bottom dry. But for a while I had an issue with chafing redness-on the tops of the legs where the elastic joins.
Basically I used disps for a week and the rash went, like you. When we tried again, another rash.
So, my advice is:
Put all nappies through a rinse cycle.
Then wash every nappy on 60 using a bio detergent. (sounds counterintuitive as I've always used nonbio , but give it ago). no water softener tablets either. Use less powder than the packet says. I use one tablet for a whole load and half a tablet for a half load.
Make sure that the cycle is the longest on your washing machine. I used to select the 40 cycle but it was only an hour and a half whereas if I choose the White cotton cycle I can adjust the temp down to 60 (or 40 for wraps) but get a longer cycle.
Then rinse in just water again. No bubbles should be seen.
Do same with fleece liners and wraps. Be careful though some wraps shouldn't go above 40.
Then try again with your little one. My DS hasn't had his rash since. I think it was detergent/ammonia build up. but washing everything at higher temp should also kill and thrush or fungal stuff too but as the rash cleared on your holiday it's probably not that.
Finally, Give your LO lot of nappy free time. Change nappy frequently too- I sit LO on a potty regularly to catch a pee here and there and that tends to extend the wear of a nappy for up to an hour. I also don't use wraps at home - just the nappy - and no bottoms as this means I'm more vigilant about when he needs changing.
Hope it improves, it's gutting when it happens but all is not lost.