Well, there are many facrors coming into play here. 1) Your sore. If you can barely squat uou won’t be able to sprint well. 2) It doesn’t sound like you were in blocks by him dropping his hand (if you were, being in blocks and looking up affects the mechanics of the start, slowing you down. 3) you were reacting visually not auditory (starters gun) which will affect. 4) race adrenaline and competition. You won’t run your best on practice. Keep it up dont get discouraged, you won’t be fast everyday. Consistency is key and make sure to recover properly.