Try feeding that YT some more - his belly is kinda pinched - they could likely both use a little more grub. frozen mysis, marine cuisine, formula 2, Rods food - and if you have any selcon, put a couple drops in one teaspoon of water and soak some purple or green nori in that for 5 min before feeding to them. The pits in the YT look like some HLLE - but that could be attributed to stress in qtine so long.
Well - the 1st I'd do is drop that sg back down to 1.008, in 3 events, about 12 hours apart. Remove enough QT water and add straight RO/DI with a tiny bit of buffer in it to keep the PH up. I suggest dropping it once in the AM, again in the PM and finally the last morining. Test PH once per day during salinity change, from then check PH every 2-3 days. (refractometer required to accuratly set sg)
2nd, raise that copper level by .5-1 ppm as soon as the tank is at 1.009 MAX, 1.008 better. It's gonna be a requirement that these 2 steps are done ASAP - and accomplished within 36-48 hours. DO NOT come down with SG slower than suggested, as ich has a tendency to survive the next "hatch" at a lower SG than the previous one could, and it only takes one or 2 to successfully feed to continue the entire life-cycle...Qtine tank temp should be 78-80, and not much hotter.
Continue this treatment plan for about 1 week, then you must be ready for a big maintenance event on the QT. What's gonna happen about 7 days AFTER the sg is at 1.008 AND the copper has been at 3ppm will require a total breakdown and reset of the tank, fish in buckets for a little while, stearlization of the entire qtine tank/filter/powerheads/PVC/heater/etc with HOT tap water. A 100% waterchange, with new sw at the previous tank SG, and replacement of the copper at previous level, new filter media, etc. (this event will eliminate ANY/ALL cysted ich, and is the first of 2 similar events) I'll provide exact details on the next segment of treatment later on.