Changing to different puppy food

Mojo our Golden Retriever pup is 4 months old now.
He came to us on Eukanuba and huge amounts of smelly
poop, so I changed him slowly to Orijen LB puppy which
has been great. However as it's very concentrated he
gets small portions & is always hungry, its so protein high
I worry about giving him any extra bits of meat. So I've
started to gradually change him over to Barking Heads
LB puppy. He's been a couple weeks on 75/25%, now its
50/50% (using the charts from each food) Now I've run
out of Orijen, need to buy a new bag (££!) so I can take
a bit longer to change him over. I'm wondering
if it would be ok to feed say Orijen in the morning,
a mix for lunch & BH for tea - rather than mixing them
each time. Or would this be a bad idea?
Also how have others got on with Barking heads puppy?

Giving different foods seems fine to me - I used to do that sometimes to give Rocky some variety. Though perhaps it might be better to find food that fulfils all your criteria but has different flavours you could try?

Personally I would opt for a 'species appropriate' food