You probably turned Combo assist off at the character select screen on accident. Go into your control scheme and turn Combo assist back on. Or turn it on at the character select screen.
The difference between Orchid and those characters is that her Ultra is initiated with the 3 Kicks (Default Left Trigger on controller), while those characters use Punches (Default Left Bumper). Different characters may have either 3P or 3K as part of their Ultra input, so the command varies between characters.
So rather than using Q, which seems to be your 3P button, use whatever you have bound as your 3K button.
Best way to ultra is to keep B’s instinct. Shadow into an ultra use the 3-kicks (HML). Than right before you finish the Ultra with the upper fire cat, cancel the Ultra the way you would shadow counter. Make sure you are at a wall. Once your victim wall bounces squat and tap the low quick kick then do shadow flick flack then another ultra. As you are doing this ultra make sure to cancel using your instinct do a shadow move or two again than do another ultra. You have just done 3 ultras with B.Orchid. The wall bounce technique, however may only work on some stages.