Yes, there are many things to be concerned about, but let's look at the entire picture. The Twins have a winning record at the break and a small lead in the division. This is primarily because they have a good lineup and their pitchers overperformed for the first third of the season. Three position players with less than a years experience have looked promising--Miranda, Kirilloff and Larnach (now out with injury)--and three pitchers with less than a years experience--Winder, Jax and Duran--have done well. Luis Arraez continues to show he is elite as a hitter and Jorge Polanco is giving indications that he'll have a monster second half to his season.
Now to the minus side of the ledger. The rotation, which looked suspect coming out of Spring Training looks suspect again after encouraging performances early in the year. Sonny Gray hasn't been the same since coming off the IL the second time. Joe Ryan isn't dominating although he's really held his own and everyone else in the rotation is both limited in upside and an injury risk. The bullpen has been poor and prospects for improvement from within are close to non-existent. While looking at individual performances from the position players, there aren't many, if any, disappointments, the offense hasn't sustained above-average run scoring for more than a series at a time.
For the second half (post All-Star break), I believe the Twins will continue to score runs well above average and they will continue to be a decent defensive outfit, barring devastating injuries. If they can find enough pitching, they will be in the hunt for the playoffs and a division crown. If not, they will continue to fade.