Initially, the symptoms of overwatering and underwatering are nearly identical. Underwatering of newly or recently planted plants tends to be a very common issue and if you are certain any previous drainage problems have been correctly addressed, then I'd lean to the plant just needing more water. But I'd want to be very certain of good drainage before I leapt to that conclusion :-)

Less frequent but quite deep, thorough watering is more beneficial than frequent light watering.

What is the best way to check my moisture level? I don't want to fall into last years trap!

Insert index finger to the second knuckle inside the rootball. If hot or dry, water. If cool or moist you're good.

tj