this is my experience  with   a similar problem & also  Jedjackson could be right , but i have cured a lot of things with good nutrition, so here is my story = i bought  a year old hen  from a breeder,  a top  laying breed like your RIR , i put her into quarantine for months ,  just to make sure  she  was  well and to keep my flock safe from any unknown illnesses  she could have ,  she never laid an egg for all that  time, then she would lay an egg  every once in a wile , this went on  since 2014 when i got her at 1 year old , then  last spring  i noticed she  was laying more eggs then her usual,  and  it was not until  this past august  that i noticed  she  was eating the cat food i leave out for my new cat,  then this hen  starts laying  an egg every other day or so,why would that happen...? the only thing i could think of is its got to be the cat food..?  she may have had a  nutritional  problem all along, and i feed my flock well  sprouted barley  & a good quality layer feed &  hi quality  vitamins  some  hard boiled egg & leftovers & what ever else i have around  fruits  & veggies and they free range , so you never know, but  one thing it  cant hurt to try  a bit of  dry cat food & you could also try a  bit of  mashed up hard boiled egg in her food and see what happens..? my other hens  never ate  the cats food  so when i saw her eating cat food  it was a bit  unusual  to me, and  since she started eating  cat food , she  starts laying eggs, so  i guess it worth a try,