Are Fw Shrimp Known To Harrass?

[Ft fisher]

Hello all! 3 weeks ago I added some FW shrimp to my tank along with some guppies, i added too many at once and had a few problems and lost a few fish, all of that is now sorted thankfully! I've just today got back from a holiday in Spain and as i sat watching my fish feed i noticed the shrimp going to the surface, eating the food and chasing the fish in my tank, the shrimp i have are pretty large, the biggest being probably about as big as my guppies if not a little bit smaller, and the other 2 are only a faction smaller than him. I thought it was rather strange and on closer inspection of my fish a few have what looks like chunks out of thier fins. Could it be due to the shrimp? Could it be fin rot? And if it's fin rot can i treat them in the tank and the medication not affect the other fish (i have no other tank to seperate them) Any ideas please?

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If it helps with anything, i don't know the species of shrimp but they are all see through. Don't know if this will help any, but just incase!