Can't help you on the stuff you are mixing with the hydraulic fluid but I assume you are using Red hydraulic fluid or transmission fluid. Put some in a spray bottle and while you have the jacks all the way extended spray them from top to bottom and retract them. Do this several times and see if helps. I don't have your brand but they use Red hydraulic fluid and I spray them down. Use a clean cloth once you get them lube and wipe down the piston. Do this once a week before you retract them and they should last a very long time.
It might be time to flush your system and put in some new fluid. The seals do dry out so yes they need some clean fluid on them regularly .
I Just check their web site and they use hydraulic fluid so you could try a full synthetic transmission fluid of your choice and you should see some good results.