Pets attacking each other

Hi Sunny .My pack at home have started attacking each other .A male and a female gang up to attack one of the males .I have indies at home and all of them have come to me at different times .The one who is attacked is my oldest who came to me when he was just 2 months. The female came to me at 1 year of age and the other male came to me when he was around 6 years .They are very friendly with humans and were ok with each other too but this is something new .Please help as i am at my wits end

The dog who is being attacked, does he get fearful or nervous?

How many walks do these dogs get?
Do they go on a walk together?
Do you follow any schedule to feed them?
Do they have their separate places to rest?

Let me know.