Correction deeds in size of plot after 29 years of purchased

Hi, My father purchased one plot around 4800 sq ft,in size nearly 29 years ago, Now seller arguing that mistake had been made by their architecture 29 years ago in plot drawing, not only in our plot but in other plots purchaser from society on same land also, our plot size reduce by nearly from 4800 to 3800 sq ft, we haven't got any notice from Authorities still. I asked society there is bigger road provision or such thing from municipality,he said nothing. I strongly suspect, society seller of plots making some fraud, by making corrections deeds in reducing our plots size, because in 4 acres land reducing 1000 sq ft from each owner means to much land price, Sir, can you tell us that correction deeds after 29 years in plots size is possible, what should we do ❓