Should i be concerned that my 4 mo old (2 1/2 mo adjusted) is hitting all milestones but is not reaching for objects yet?

No: Reaching is a typical 3-4 month milestone. If your infant was a premie, be patient. Stimulate him, though, with objects that are brightly colored or make noise to perk his interest.

Use corrected age : for attainment of milestones. Encourage prone position for play, putting a bright toy in front of baby, then to each side to promote getting head up 90 degrees at 2 months, head & chest up at 4 months. Physical & occupational therapists at your state's Early Intervention Program can give you tips during an assessment , http://www.health.ny.gov/community/infants_children/early_intervention/,