looks a little thin to me, nothing serious though, I would give two rats next feed appropriate size for him of course its hard to tell from the pic how big he is.
You will see a few bloods (not on here though I doubtlol ) that show little spine and are just far too robust and fat resulting from over feeding or ignorant owners not knowing any better.
Your just looks like it needs a good feed maybe for the 1st month, then cut back to every 7 days a large enough meal, my adults get fed every 10 days or 14 some times which is fine for an adult blood feeding on large rats.