2 yr old female GSD – constipated – Dry dog food recommendation

Hi folks,
I have a 2 yr old female German Shepherd (about 65 lbs) who I’ve had a very difficult time finding a dry dog food that she will eat. About 3-4 weeks ago I switched to Victor Hi-Pro and she loves it (finally!) However, a side-affect has been terrible constipation. I mean her poops are super hard and I can see she’s having a hard time. I started adding a lot of warm water to her food to try to make sure she’s getting enough water (she’s not a big water drinker, even though we change her water throughout the day and make sure it’s always available). But that wasn’t working, so I read about adding canned pumpkin to help. I started this 2 days ago, gradually increasing it to about a half a can. I can tell it’s helping, as even though her stools are still hard, they are slightly softer than they were. Also, she keeps biting at her tail/bum area, and it looks a bit red down there, which I imagine is due to the irritation in the anal area due to constipation, but I’m no vet.

Anyway, all that is background info to ask if anyone else has had a similar experience and if so, did you switch to another Victor formula that remedied this?

I’m hoping for a simple solution, like just switching to a different Victor formula (and not having to do the, “get these really hard to find ingredients and blend them up a special way, preparing a week ahead of time…”-type stuff).

Would love to hear from anyone who’s had a similar experience and found a solution.

Thanks!