75G Cichlid Tank

Hello, new to the forum. I am new to keeping African Cichlids and in fact this is the largest tank I have managed. This tank is a 75 gallon and I bought it from someone on facebook marketplace about a month ago. The person stated that all of the fish (peacocks) have grown together since juvenile. I felt like the filtration was lacking so I bought an FX4 to add to the Seacham 110 HOB I believe it is. After doing some research, I'm not sure this tank is big enough for the fish in it, especially the giraffe. To my best knowledge, the fish are

1 X male Giraffe Cichlid (Nimbochromis Venestos)
1 X male Strawberry Cichlid (Aulonocara?)
1 X male Blue Cichlid (Sciaenochromis fryeri)
2 X male Electric Yellow Cichlid (Labidochromis caeruleus)

I may be wrong in these classifications though. So far, they are all doing ok except the giraffe chases the others quite often, especially around feeding time. He seems fairly aggressive but not sure. I feel like I need to rehome the giraffe but not sure again. Any help is appreciated!

Thanks again!