Management is still going to be the first productive step here -- meticulously keeping them apart so that there aren't ever any opportunities for random pieces of kibble to end up on the floor (feed them separately then carefully check for random dropped bits of food. Feeding in a crate can remove the concern that kibble has scattered plus you can easily clear any dropped bits out and close the crate door. Toys or treats should be offered inside crates or in two separated areas (eg with a baby gate or closed door).
Just as important: I'd urgently begin doing some training to help avoid food and resource guarding generally, as this sounds like it's escalating into a pattern. This is some of the most important training to do with all dogs, as resource guarding can develop into a serious and risky problem for the humans, not just another dog. It's one of the main reasons dogs are surrendered to shelters. I just helped rehome a cavalier that had developed a resource guarding issue that had resulted in some bites
but this dog is now in an experienced home after he was professionally assessed by a trusted trainer, as having a guarding issue that could be addressed still as thankfully, it wasn't too advanced. But his former home was no loner suitable as small children visited.
I'd start here, right away, with expert Dr Ian Dunbar's advice on resource guarding:
I really like this trainer's website too and over the years have often recommended her advice. Try:
www.diamondsintheruff.com
A good trainer could also help you here and if you want that option, I'd recommend using the CCPDT website
https://www.ccpdt.org/ where you can search your area for a qualified trainer if you wish to look for help.
What you're seeing isn't alarmingly abnormal but it is behaviour that must be very carefully managed, especially around an older dog who could be hurt, and addressed with training. What's happening between the dogs could start to be directed towards people, without some work here while it's still a minor squabbling issue. You're at a good point to intervene 1) to prevent these encounters happening at all and 2) to start working with your pup on preventing resource guarding. Hope that helps.