Yes scaleless fish are very sensitive to chemicals. I wouldnt grab the chemicals yet. Check your ammonianitritenitrate and ph levels. Do a partial water change accordingly to help boost your fishes’ immune system and see if their behaviour
improves.... chemicals should b the last resort
Praziquantel is a fairly safe wormer. I’ve used it on tanks with Queen loaches and dwarf chain loaches.
However, I don’t recall if it’s recommended to use a half dose with sensitive fish so *please* read the directions.