Possible under feeding?

I've had my tank up and running for over 2 years now. I haven't lost a single fish in this tank. I used to have nitrate problems so I started feeding every other / every 3rd day. I upped the amount of food I put in too.



Anyways I started doing this about 3-4 months ago. I didn't notice any side effects really. The past month though I've lost one of my antheas and today I lost my mandarin. I saw that he was getting smaller so I would spot feed him every day and at most every other day. He took frozen foods, dry foods as well as pods I would buy. I haven't bought pods in a while though as they are breeding really well in my sump I figured they were making it into the display as well. Plus he was eating frozen foods so I didn't think it would matter.



I checked all my params and they are identical to what they always are



nitrates ~ 5

nitrites - 0

ammonia - 0

ph - 8.2

salinity 1.026



I haven't switched anything or made any changes. I haven't added anything into the tank in a while. I do bi-weekly (sometimes weekly) 20% water changes using the same salt and rodi water that I always use.



The only thing that has changed as the feeding schedule do you think that could be it?