They won't lay in nest boxes?!?!?!?!
This is not uncommon when they first start to lay - a large part of it is that the experience of laying is all new and a bit confusing to the birds. They often seem rather surprised and caught off guard when an egg drops - or will spend all the time in the nest waiting and then panic at the last minute and hop out to run around and drop the egg wherever they end up. It's a bit early yet to worry too much about it, imo, as they usually start to get the hang of it as long as the nest boxes are appealing, easily accessible to them and look like a good place to lay an egg - perhaps if you post photos of the inside of your coop so we can see what they see we can help you be sure that is the case.
Nest boxes are normally a devise to make egg gathering easier on the chicken keepers. When your nest boxes suite your birds at least as much as they suit you then your hens will use them to lay in.
I had one hen that decided an outside sink was a good nest - when she went to the sink, i picked her up and put her in a nest - she got the idea, but as other members have suggested - they are young and so probably have not got the hang of this egg-laying business - they will sort themselves out pretty soon i would imagine.
I know different breeds will start laying at different ages. I've read between 5~7months depending on the size. I have RR and Barred Rocks. They are approximately 6months old. I'm concerned they haven't started laying yet. I live in Florida so this time of year it's getting dark about 7pm, will that delay my girls from laying? I've had chickens before but this is my first time raising them from biddies.
I can't imagine that darkness falling at 7pm should be an issue. I live in Kenya, where we have 12 (and a bit) hours daylight every day of the year. By 7pm its dark and mine lay all year round.