CF, on the ich. Clown Loach
are notorious for ich. Some fish are, hatchetfish is another that comes to mind. Treatment is important with such fish because the ich is tough and can kill them.
Raise the temp to 85F. I do this partly via a major water change (half the tank) increasing the temp a few degrees with the refill, then adjust the heater for the rest. Given the severity with these fish, I would then add CopperSafe, at the dose on the label. A small bottle will suffice, you only use it once. It is effective for 30 days, so just leave the tank (= no further water changes), feed sparingly but normally, no other changes. After 10 days, turn the heater down to normal and let the tank naturally cool down. After another 4-5 days, do a 50% water change. Everything is normal from there on.
This is the safest method I know, and with my sensitive wild caught fish (including hatchetfish) it has always worked. You can also handle ich with just a rise in temp to 90F, but only if all fish can manage, and some of yours (Congo for one) will have considerable difficult at 90F. The 85F for a week should pose no problem, I have never had "cooler" fish die from this.
A QT is wise these days. For over 12 years I never bothered, and never had issues, except ich maybe once or twice. No days, it seems every fish I bring home has something, and I now have a 20g QT tank with spare plants running that I use as QT. I have had minor ich with just about every new fish these days. But also had things far worse, protozoans. Fish stock seems to be deteriorating, so a QT for 4 weeks is wise.