This year was supposed to be different for Kodai Senga. He said he felt healthy during spring training, was throwing hard and expected to get back to the form he showed as a rookie with the Mets in 2023. But just like pretty much everything else in Queens this season, it hasn’t gone as planned. The right-hander is back on the IL with lumbar spine inflammation and won’t throw for a week to 10 days after he received an epidural Tuesday. When the right-hander might return is anyone’s guess. Senga said Wednesday he’d been dealing with at least some form of discomfort in the area as far back as spring training, but it wasn’t until his most recent outing against the Rockies on Sunday that it became clear he couldn’t pitch with it.  “I was able to manage it, [but] it got to a point Sunday where it was definitely affecting my pitching and I had to bring it to their attention,’’ Senga said through an interpreter.…