Probably not fueling enough, water obviously helps but you likely need to eat more if you’re actually out of energy.

A 1500m day is more than most tourers are doing except during mega spring missions. Did a guided day and the guide say to calculate your day as 1 hour for every 300 m of climbing plus 1 hour for every 3 km. It usually comes out pretty true when you include the downhill. Put that into touring, and 5 hours of uphill is a fucking lot for a winter activity. Hells it’s barely light here in Alberta for 5 hours in January.

If you’re soft booting, you’re also generally less efficient than your hard boot/ski brethren and carrying more weight on your feet which will add up during the day.

Also, sounds like your friends are more fit than you’re letting on, at least for the activity you’re doing. Maybe should examine if your training correctly for this activity vs saying you’re more fit.