[HELP] Redirect whole page to another (301)

Hey everyone, I got these two online shops and they both are in the same niche. Lately, one of them starts to drop in rankings so I decided to focus on the other one and shut the poor one down.
Is it a good idea to redirect the whole shop to the more profitable one ? Like putting a 301 to redirect all pages to the new shop.
Or will this harm my other site because of so many new backlinks (passed from the old domain via 301)??