At 18 months old, and at this time of year. prior to moult, they should be laying daily. Have just checked your post again, and you say that you have only had them a week. Generally, if I buy in, or indeed sell a hen in-lay, I recommend that you wait at least a fortnight before expecting results, as a move of house and a change in environment can put them off the lay for quite some time. An example would be some hens that I sold, and had them returned and a refund demanded after one week (despite the fact that I had explained the above to the purchaser). After two weeks back with me, the hens all returned to full lay. Also, as it gets warmer, you may be prone to an early moult, so bear that in mind....
And, if all else fails, they will not be brilliant as a whole bird for roasting, but will probably joint up OK.....
Good Luck.