Retarder House Fly Infestation?

Hi there, I'm new and I'm not totally sure of all the protocol on these forums but I have an interesting issue, my plants seem to be nirvana for brightly colored but extremely slow house flies. My plants are in their 5th week of vegitative growth and are about 2' tall. They are being grown indoors, in soil under a 400W MH lamp. About three days ago I noticed a couple flies buzzing around the plants. I killed them and the next day there were at least a dozen buzzing around. I disposed of them and put up a fly strip but more have come. They don't seem to be hurting the plant but they do love to sit on the leaves and for some reason they are incredibly slow (probably why they're so easy to kill). Anyone experience this before? Anything I should be careful about? These aren't white flies. Thanks a bunch.

Are they little flys or big old house flys?

These look just like big ol' house flies except they are shiny gold in color and VERY lethargic.

Dunno never heard of them,we obviously live in diff countrys

Maybe they're just lethargic from the weed? lol. Try spraying some Pyrethrum. It kills insects on contact and is not harmful to mammals.