Is there a way to help a bird with Trich?

Hi,

I just recently started getting a few Chaffinch in my garden the last few months and this past week noticed one acting lethargic (slow to move and also just sitting around). I’m from America, so wasn’t sure if this was common for this bird, but none of my other birds act this way so I looked it up and I’m pretty sure it has Trich. 
It seems to be having difficulty swallowing or digesting its food and sits around a lot. I went outside and was startled to see him still there (wasn’t flying away like all the other birds). 

I have dumped all my bird baths and sanitized my feeders.  I have dozens of birds that come all day long, so it breaks my heart to think of taking all their food/water away (which I saw was the recommendation), especially with this cold weather. The chaffinch seems to be mainly ground feeding anyway. Is there anything I can do to help it? I did see what looked like a red kite swoop through this evening, so maybe he put the poor little guy out of his misery.

Any recommendations on ways to help would be greatly appreciated! My birds bring me so much joy each day!