Not printing infil

[Johnmgg 1]

Hi all, I have a quick question: I am trying to print 8 rods (5.7mm in size each). One of the rods came out great. I am printing in PETG. I can bend the rod and it never brakes. Basically what I want. GREAT! The other RODs just crush with one finger. I printed the 8 RODs flat on the bed with a brim. I printed 2 more with different filament to test. I see that the 2 rods printed as test Vertically did not get filled in with infill. Do you have any ideas. I can tell because it did not print the top or botom of the rod only the wall you can see straight through it. I was thinking that maybe my RODs are to small for infill to print. Do I need to print these as walls only or something like that. But it confuses me that one of the rods did get infill printed? Also could this be a temp issue as well because shouldn't it still bend not brake even with a thin wall?