Will you be running six simultaneous round robins or are there some games between levels?
Is each team to play 26 games? A straight round robin will have an odd number of rounds (e.g., 10 teams need 9 rounds to play once against every other team. If nine teams, each team will be idle once and it will still take nine rounds.)
If you have an odd number of teams any round robin table can be used--ignore the first column (that team has a bye) and randomly assign the rest of the columns with half of the days of the week needed like five Sunday, five Monday, and the rest Tuesday. With an even number per level, check out "Court Balanced" on this website.
HTH
P.S. Do you have 14 teams per group playing a double round robin? If so ignore the 2nd paragraph.