Usually if the rents are that far below market there is a clear reason...either an owner that is afraid of losing the "good" tenants, or a property that is notably sub-par for the market.
Raising rent, local legal restrictions notwithstanding, is simple and should be one of the first steps you take upon acquisition, at the earliest lawful point. Sure, you need to consider market timing, available tenant pool, and actual property conditions.
You are running a business, correct? Does the local grocer keep prices low so not to offend or cause hardship to customers? Does the gas station hold their prices down? No, and no. Only weak rental managers do this. Reevaluate every year by reviewing conditions, market, tenant finances, and inquiring of tenant's intentions.
Whether you just waited to long, or just acquired the property, immediately inspect each unit to determine actual condition and housekeeping of current tenants. Obtain a completed rental application from each adult. Evaluate, by walking through, nearby competition and reassess your pricing. Evaluate the DTI ratio of the tenants. Depending on remaining term of each existing tenant, and depending on what is needed in terms of rental prep, provide adequate reasonable and lawful notice of your plans. If the unit needs updating, this is simple, you will be renovating and can be more flexible on a move date, charging only for days occupied. If the unit is actually great, but the tenants not so much, if their application does not pass, simple...they do not qualify for the planned rent increase. Allow for additional time for these folks to relocate...60, maybe 90 days, or even wait for spring or end of school year, whatever will make it easier for them, while not leaving you standing in a snowdrift.
If market has truly not moved, or moved downward, without some artificial catastrophe like covid, then you don't make an adjustment that one year.