Be specific. What are you concerned about? That he's hurt? That he's regressed and is now a worse player than he was a month ago? That he's going to shoot 31% going forward?
I'm genuinely asking, because if it's not a short term shooting slump, I really don't know what the alternative could be. The larger sample suggests he's a first team All-NBA level player and one of the best 7 or so basketball players in the world. Poor raw shooting numbers in six games out of a random ten game sample is not a persuasive argument that that's no longer the case.
Let's flesh the argument out a bit, then.
There has been discussion this year of whether Tatum is being given too many minutes and whether playing him too much creates any risk of having wear down and not be in top form come playoff time.
It has been observed that Tatum is at near the very top of the league in total minutes and minutes per game, and that his workload is higher than basically all of his fellow elite peers (guys who were All-Stars/All-NBA players).
So there's no argument about the workload being very high for current NBA standards: it simply is; almost all other stars asked to carry their teams to championships don't get this workload in tyoday's NBA.
A more debatable is whether Tatum can handle it. Since entering the league he has certainly been one of the most durable players in the league, and durabulity is an ability in and of itself (see James, L.).
Another thing to consider is that Tatum is as much a 2 way player as any NBA star. He's a key part of what the Celtics are doing on both offense and defense. They don't "hide" him defensively because he is so integral to the offense, they depend on his rebounding, they will often match him up with opposing stars, eetc.
His 10-game skid comes right at the 3/4 mark of the season, so it fits right in line with what people concerned about his excessive workload might expect to see. It's not proof of anything, of course. As has been discussed, his 10-game skid isn't obviously out of line with similar struggles of other great players. But that's also not proof of anything.
But here's another thing: one of the key improvements Tatum has made to his game this year is getting to the line a lot more. In the past 2 games he has attempted just 3 free throws, and one was a tech. There isn't a 2 game strech all season where he attempted fewer FTs - his prior season low was nine FT attempts in 2 games. (Last season, when he took many fewer FTs over all, he only had as few as 3 in 2 games one time. ) So his bad games and poor shooting from three have coincided with his abandoning the drive. To me it fits (though does not prove) the "worn down" argument.