Sorry, let me see if I can expand on it. I had to brighten up imaged in LightRoom by about 1 full stop, unless I raised my flash power to +2 (my flash will go to +3 at 1/3 increments) those numbers are using the ETTL settings, going manual I can do the standard 1/8, 1/4, etc... When using my 7DMKII with the same camera settings I was usually at 0 or -1/3 on flash power. That shot was in a controlled situation as well, I found the grasshopper outside and brought it in, put it on some cut flowers and had two external lights to help the flash, which is my usual setup for indoor shots, and one that I've used hundreds of times with the 7D2. Now, I'm still going through all the settings...maybe there's something I've missed, or maybe it was just this specific case, as I've only shot with the 90D once at this point. I'm waiting to find a jumping spider or two to test again, as they are my normal subjects for this stuff.
Here are a couple shots with all the same equipment but using the 7D2