Oh no. (((Hugs)))) poor little guy!
Sounds like he might have allergy shiners? (the puffy eyes with circles/bags under them) That's a big indication that something is bothering him.
I think it's fine you took him off all solids, but things that he has been on for a while, with no issues, you could start to reintroduce first (but I would wait a couple weeks to have everything clear out),.
It is possible he has a rice sensitivity/allergy - my DD2 did.
How long has he been on the Alimentum? Alimentum/Neutramigen still bothered my DD2, and we have to supplement with Neocate, which is amino acid based and further broken down so they can tolerate it. However, we knew w/in the first couple of weeks that the others didn't work - how long has he been on Alimentum?
Do you have a ped allergist? Or a ped who is familiar with his history? I would suggest getting an appointment and discussing some basic testing to see what else may be bothering him.
The thing is, it will take a week or two for the offending food to be out of his system (depending on what it was and how much he's ingested). So if he's been on rice for a month and never had an issue, I wouldn't pull it. But if you are unsure, starting from scratch and getting a safe baseline would work.
If you pull him off everything I'd say it give it at least 2 weeks. Probably 3. Until you start seeing good diapers and the symptoms are gone. Then start very slowly with foods that didn't seem to pose a problem before. Introduce each food and wait a full week (this is how our ped allergist had us do it).
It could be the formula, but if he's been on it for a while, probably (hopefully) not,.
Sorry this post is all over the place, running out the door, but wanted to post quickly.
