Dogs suddenly fighting

I have 2 dogs, who have gotten along together like best friends for 2 years. Suddenly this week, the bigger one keeps lunging at the smaller one and biting her. It’s not their usual play fighting, she yelps and won’t even play with him anymore because she’s scared. How can I stop this behavior? I know everyone says reward based training is the best, but how am I supposed to reward him for not biting her? He’s been jumping at her maybe 3 times a day, and it’s increasing. I thought it was over toys/bones at first, but he’s started doing it randomly. Should i spray him with water? Yell? I know people will say get a trainer, but my whole state is shut down right now and we’re quarantined.

I was putting on their leashes to walk them just now, and he jumped on her and grabbed her by the neck! I yelled at him and decided to only take her and walk them separately, but she wouldn’t go without him (go figure 🙄)

He’s also been barking a TON at night! Is it quarantine? Is he bored? he’s getting a lot more attention than usual because everyone’s home, so I don’t see why he’d be bored.