Hi , I'm no expert but I'm sure you can't treat with chemicals because of the clown loach.One way to treat is to increase the temp to about 30-31 which helps stop the white spot getting worse but make sure you have good aeration because oxygen levels drop in higher temps.I've heard you can treat with salt but I have no idea about dosing levels.Try a search on this and other sites for that info but I would definately up the temp if you are sure it's white spot.
Scaleless species are very sensitive to salt and it should not be used with them. It is only copper medication that is harmful to scaleless species such as Loaches, these can be used in half-doses. Upping temperature just increases the metabolism of the parasite, makes it die faster but also makes it breed faster when there is no medication.