Toilet training regression

Both my 1.5 yr old and my 9yr old staffies are toilet trained but the last few weeks they've been going to the toilet in the house. I don't know why they suddenly seem to have forgotten their training, and I don't know how to fix it.

Hello and I'm sorry to hear that you are having this problem; it can be upsetting and emotive when dogs urinate or deafecate inappropriately, not to mention stressful.  There are some specific things that can give you clues as to the cause, but I have little to go on here.  First of all, it is important to define what is meant by toilet; do you mean urination, deafecation or both? - as the rules are different for each.  Secondly, it is important to define the circumstances in which it is happening and any changes that led to this.  Was there an occasion where access to the toilet was lost?  Is it cold outside?  Are they going more frequently, or just in the wrong place?  Increased urination for ample, can be a medical problem eg if both dogs get renal failure at once eg due to toxicity.  It can also be scent marking eg in response to a behavioural change or local female in heat, or a reflection of access to - or willingness to access - the outdoors.  It sounds as though a good idea would be to let your vet check urine samples in case of illness and to write down what you can for your vet aboyt their recent history, especually around the time the change took place.  Frequently, something in that lot will offer some clues.