The tourists fell to a 125-run loss at Trent Bridge which followed a four-wicket defeat as India went 2-0 down in the five-match series.
Gambhir's charges have now lost all four of their completed matches in the shortest format since the winning the T20 World Cup on home soil earlier this year, including a 2-0 clean sweep against Ireland.
The made the decision to revamp the squad with World Cup winning skipper Suryakumar Yadav dropped while player of the tournament Sanju Samson has been left out of the side for last two matches.
Gambhir said: "When you go to reset a side, sometimes you get such performances. There are a lot of changes from the XI that played the T20 World Cup final to now.
"Be it the captain, be it the opening batsman. There is no Hardik Pandya, there is no Jasprit Bumrah.
"When you go for that reset, it takes a bit of time. If you see, a 15-year-old is opening, Prince Yadav is in his second T20I, Harshit Rana is coming back from an injury.
"We ultimately look only at results, and no doubt results are important in international cricket, but we have to be practical as well. Sometimes you give players time to develop.
"England is a high-quality side. If you put players in against such teams, you have to give them time to develop. Because after a reset, things take time."
The fourth T20I against England takes place on Thursday in Bristol with India needing to win the final two matches to level the series after teh first game was abandoned due to rain.
England fast bowlers Josh Tongue and Jofra Archer shared seven wickets to condemn India to their heaviest ever T20I defeat as the tourists went down by 125 runs in the third game of series at Trent Bridge.
Vaibhav Sooryavanshi became the youngest debutant for India in international cricket but England prevailed by four wickets in the second T20I at Old Trafford to go 1-0 up in the five-match series.
The England Cricket Board has revealed its 16-strong squad to take on India in a three-match ODI series.
India assistant coach Ryan ten Doeschate admits the squad are in "disbelief" after suffering a shock T20I series defeat to Ireland but offered "absolutely no excuses".
