Dog and Cat with Kidney Disease: Pica

My two boys have been diagnosed with kidney disease. Our cat; George is in the advanced stages - stage 5, our dog; Socks, is in the early stages. At 2230 on May 22nd Socks suddenly started throwing up. I thought it was blood and nearly had a heart attack, but when I had a closer look I saw that it was mostly dirt, bile, and water. We went to let him out so we could clean, and as he went out George followed (he is not an outdoor cat). I followed him to the garden where he appeared to start eating dirt as well. I did a little bit of reading and found out that this particular type of pica has mainly to do with iron levels, and lack of proper nutrients. Both of them have had to switch diets, George has been struggling to eat for the past 2 weeks and we are picking up a bag of Royal Canin Renal Diet for cats tomorrow. Socks has been on the Royal Canin Renal Diet for 3 months. My question is; is there anything we should be doing? Are there any supplements I should be giving them to help them get what they need? We're having such a hard time with this diagnosis for the both of them and we're trying our hardest to make them comfortable in their last days here, but every corner we turn a new page and it's never happy. Whether it be incontinence, throwing up, hairballs, no appetite, it seems every day is a new thing and it's breaking my heart. I just want to help them, but can't afford a vet visit for each of them every time a new symptom arises.   For reference if needed: George is a long hair domestic, aged 7 Socks is a purebred Border Collie, aged 12

Hello and thankyou for that useful history.  There are, however, a few leaps that I'm not following:  eg, Socks the Border with Pica:  you've done some research and apparently this particular type of pica is to do with iron levels.  Please can you explain what research you did and why? - as I cannot understand how you got from pica to knowing for sure it is caused by lack of iron.  How did you reach that conclusion?  A vet would probably need to do bloods and a thorough history and then maybe even further samples or scans to reliably get to the bottom of the reason for pica, unless you know something I don't (eg maybe your dog has been following a vegan diet for years, so you concluded that iron must be lacking, or something like that?) Reasons for signs like pica can include liver disease, diabetes, cancer, mineral defecits, hyperthyroidism....  furthermore, the garden dirt vomit concerns me because sometimes digested blood can look exactly like that.  Have you definitely seen Socks eating soil? I agree that a lot of dogs dont need to go to the vets a lot but I'm afraid that Socks potentially needs some further investigation / questions to be asked - pica is generally a fairly serious sign.