Mathew.....a lot depends on which Cacti you have but as a general rule, free draining compost with grit rather than perlite is probably a better bet. Until you are sure of what exactly you need, I think Welsh Onions suggestion is a good one.........either buy the Cactus compost or note the makeup so you can DIY so to speak. A good basic feed is Phostrogen but you need the correct growing medium too
What exactly do you mean by "spike loss" ? I've not come across that in the years I've been growing them. Perhaps a photo may help to elicit more advice.
I use tomato feed to my cactus as my own feed is to smelly for indoors
When I grew cacti and succulents years ago, I fed them occasionally on Phostrogen. I think spike loss might refer to succulents rather than cacti?
Mathew..........."maybe it's just old age ? ".................Comes to us all unfortunately
I have a lot of cacti and make my own compost from standard peat-free garden compost, sand, and grit to a ratio of about 70/20/10. As for feed the general rule for cacti is either a general purpose plant food, or tomato feed at between a quarter and a half of the recommended dosage for other plants. If you go above that the cacti will become mis-shapen due to over-feeding.
Between October and the beginning of March cacti should not be watered or fed as it's their dormant period. if they're in a particularly hot room then you could give them just a little water occasionally through that period.
I has just dawned on me that you mean spine loss rather than spike loss! Duh! I was thinking flower spikes on succulents rather than spine loss on cacti!
Hogweed......I confess I was wondering what "spiny" succulents you were growing. I just assumed spike meant spine in this particular case but I could just as easily have been wrong
Still haven't come across the problem before......in my experience, even if the cactus dies off the spines still remain enough in evidence to be a literal pain in the finger