bathroom caulking

i just remolded my whole bathroom 3 months ago, and i notice in the tub area, the caulking by where the tile meets the tub is starting to crack in some areas, not much. my questions are should I just recaulk over it? scrap it off and caulk again? should i fill my tub up and let it sit then caulk it? its a fiberglass kohler deep tub. if i do scrap it, what should i use? thanks, the caulking i used was the one from the tile store that matched my grout.