I tried looking up common skin conditions in cats on Google images but nothing seemed to match.
Basically two of my indoor cats suddenly on their backs towards the rear (area between midsection and tail) got multiple raised little “cowlicks”. One of my cats only had one of them on his back that was straight up but went away after a few days so I chalked it up to excessively grooming one spot. But my other cat now has about eight of these little raised cowlicks. The fur is standing straight backwards at a 20-30 degree angle and each cowlicks has a small bump underneath. He’s had them for now longer for a week but doesn’t seem too bothered by them, since I never see him licking or scratching at them.
Ringworm (actually a fungal skin infection) would be one thing to consider; usually causing a raised, disc-shaped patch on the skin that may appear slightly inflamed and/or rough; during the inflammation the hair/fur may not lay flat and later, there may be loss of hair in the affected patch.
Might not be that of course, but it’s one possibility to look into.
Cats respond to many different skin irritants similarly, creating a miliary dermatitis. This time of year in my part of the world, fleas are often the cause.
I’d use a flea comb and look for fleas, especially since more than one cat is involved.
About matted fur- One thing to keep in mind is that matted fur is painful for the cat. (Our Big Orange Cat has longish fur that tends to get horribly matted every summer despite our inept efforts to trim it proactively.)