The Proteas batsmen were woeful in the second ODI at Centurion on Sunday after being bundled out for just 118 with India leg-spinner Yuzvendra Chahal taking career-best figures of 5-22 in 8.2 overs.
Left-arm wrist-spinner Kuldeep Yadav also chipped in with 3-20 in six overs as the tourists thrashed the home team by nine wickets to take a 2-0 lead in the six-match ODI series.
Markram, who is standing in as skipper for the injured Faf du Plessis, believes each batsman has worked out a plan to counter India's slow bowlers and they need to just work harder at it.
The 23-year-old skipper said: "I don't think there's too much of a lack of a game-plan. If you speak to each individual in our top six or top seven, each person has got a clear plan.
"So it obviously comes down to execution on the day. Like I said, they are two quality wrist spinners and we give them credit. But I still think we can execute better, and that's the nice thing.
"It's not that something that's drastic that has to change - the plans are in place, now we've just got to keep working hard to execute that's all."
The third ODI takes place at Newlands on Wednesday with the Proteas now needing to win all the remaining games to win the series.