The air con feeling 'weak' is a sign of a low freon charge. If the capacity is 2 lbs, but the car is only holding 1.85, the compressor will still engage and cycle, the car will still cool, but it will not cool to it's full potential.
If the vehicle has ever had air conditioning repair work, you could very likely have a very small leak via O-ring. These systems run at 2-300psi, so if an O ring is not up to par it can leak relatively easily. Another thing too is that AC lines, even though they are aluminum, are prone to corrosion. On a vehicle this new, that is unlikely though. I would have your dealer do a dye check- where they look for a special dye oil under a black light. Because the freon carries the PAG oil, any leak can be detected using this, as the leaking area will be covered in this special dye (which isn't visible to the naked eye unless in large quantities)
RIP Ben "Jever" Doebele, we wont forget you
Please, call me Chadley
1997 328iS... HR coilovers, Brembo F40 calipers, camber plates... I sure do miss you
1990-somethin Chevy K3500... Twin turbo Cummins swapped Chevy, dana 60 front axle swap, 4 link rear, air ride, custom everything. 600+ hp, 1296 ft lbs tq