Feeding two dogs - help

I have had my Boston Terrier for 7 years and just adopted a 4 year old Boxer mix four months ago. So, of course they both went through some adjustment, but they get along and things are good. Except...my Boxer deals with anxiety and needs coaxing eating. She sometimes vomited when I first got her, so it was an issue of finding the right food as well. So, her food is good and some days she gobbles and others walks away. When she was sick, I would feed rice, then add some baked chicken, then work her back to her food. I tried adding water to soften, shake her bowl, etc. So, now my Boston watches me, and waits to see if I add something to his bowl and now has to be encouraged to eat. So, I am assuming I have accidentally encouraged him to be picky and I need advice on what to do with feeding them.