I have a frame I found that had been spray painted so I had it sandblasted. I did not prime it immediately so it developed rust spots on it. I got a rust converter and used it and it worked well but after I cleaned off the rust converter and was waiting on it to dry for a coat of primer it developed this light browning in about 30 minutes. Is it ok to put an etching primer on top of this or should I work to get the new light oxidation off?

I wouldn't paint over that. Mystery oxide underneath might be OK, might be a problem. I generally don't like proprietary chemicals like rust converters. IME they're meant more for old rusty iron furniture and stuff like that.

Why take a chance. Looks very thin anyway. Clean it off. Wet or dry sandpaper wet will work. Maybe a wire brush. Wear gloves. Some sort of acid based deruster like evaporust or barkeepers friend will speed it up. Test a small spot first.

Steel wool or a Scotchbrite pad, followed by wiping it down with Mineral Spirits will work to keep it from re-rusting for a few weeks. Wipe it down with lacquer thinner immediately before priming.

The only reason I used the rust converter is the finish is pretty rough after getting it sandblasted so it isn't sanding very well

Yeah, that makes sense. Textured surface isn't going to sand well. From my limited understanding of rust converters, that brown is probably iron tannate, which is OK to paint over. Or it could be some fresh iron oxide. I'd still try to remove it.

I'm thinking naval jelly and a wire brush would work. Maybe some scotchbrite. Test first.