A2344 on 5th street 8ob

[palman]

I'm relatively new at Stud8, I've played it a few times before, but certainly can't call myself good.

10/20 stud8 on party. I'm dealt 234 rainbow, and 4 of us put in $20 on 3rd street.

On 4th street, I get an A and we all put in 1 bet on 4th street. (We may have gone 2 bets, does this change the equation drastically on 5th?)

On 5th street.... the boards read as follows. No real obvious flushes out there.

A99
554
456

On 5th, the A99 leads out, 554 calls, and the 456 raises.

I'm new enough to stud that I don't know if folding my A2344 is a cardinal sin, an easy laydown, or a marginal situation. I believe the guy with the 456 caught the 6 on 5th street, and he showed aggression on 4th street. I felt 23 as his hidden cards were a real possibility, and with 3 of my wheel cards gone, and a 6 gone for presumably the best low anyone is gona make, and a wheel likely not even giving me a shot at the high, I folded. If the A99 has trips, it can get real expensive on 6th if he boats up and I don't hit one of my 4 outs. Thoughts? I apologize in advance if this is a simple question. I just thought there might be some kinda cardinal rule like "don't fold a234 on 5th in a big pot" or something to that effect.