America, the country's richest club, replaced Carlos Reinoso (pictured) with Alfredo Tena and Guadalajara-based Atlas appointed Juan Carlos Chavez after Argentine Ruben Omar Romano resigned.
Estudiantes Tecos, Queretaro and Santos Laguna have also changed coaches since the 18-team Apertura, the first of two championships in the Mexican season, started in late July.
Six points from nine games sealed Del Olmo's fate at Tijuana, though his achievements were recognised and appreciated by the club.
"The directors give enormous thanks to Del Olmo's work," said Tijuana in a statement shortly after Sunday's 2-0 home defeat by Estudiantes Tecos.
"He brought the Tijuana team into the first division of Mexican football and that is something that will always be recorded in the illustrious history of this border town."
Chilean Reinoso quit America after eight months at the helm following their 5-3 defeat to Chiapas and his replacement Tena returns for a second stint having previously been in charge in 1999-2000.
'Captain Fury', who has also coached Santos Laguna, Puebla, Pachuca, Queretaro and Veracruz, will make his debut with the Eagles against Tijuana on Saturday.
Romano resigned after only four months at Atlas after they lost 4-2 to Pachuca at the weekend, leaving the Desert Foxes bottom with five points.
His replacement Chavez led Mexico to third place at the world under-20 championship in Colombia last month.
Chiapas, Cruz Azul and Guadalajara lead the table with 17 points with UANL a further point behind in fourth.
The teams meet each other once in the Apertura and the top eight qualify for the play-off stage in a new system introduced this season.
Previously, the clubs played each other once but were confusingly divided into three groups.
