What's wrong with this picture - Canon T5i. Bad CMOS sensor or just poor optics?

Hello. First time post here, amateur photographer.

Overall I am LOVING my new camera build I did last week - a Canon T5i. The last camera I bought was the Canon 20D new probably 8 years ago, so I was long overdue for an upgrade. Primary lens I'm using now now is a Tamron 17-50mm f/2.8 (bought used) and have the Canon EF-S 18-55mm f/3.5-5.6 (new) that came with the kit. Just under $500 total.

Still getting used to its settings and shooting it but overall it's awesome.

Biggest complaint is I'm getting some color dispersion (chromatic aberrations) and assuming this might be lens, or possibly a defective CMOS sensor? Over 2 days or so I've taken 100 shots with the Tamron lens haven't shot much with the stock Canon lens yet... Any other thoughts on what the issue might be. Camera was new out of box and I just slapped the Tamron lens on.

You ll see blue fringe going from dark to light contrast and red fringes going from dark to light contrast. See the images I ve attached this is a green leaf and a black rail over a white background. This illustrates the problem pretty well. To the left of the hat you ll see a blue halo.  The more I read into this the more it appears it's a camera issue but I want to run these shots across you all here and get your input before i return the camera.

Example: Train photo close up you see some red around black/white contrast in numbers, some blue around edges of plant leaves and the hat.