Congrats!!
I'd also agree with Ducky - you've got approved for two in the same day (which will have amazing benefits for your AAoAs!), but if I were you I'd now quite while I was ahead. For now. If you keep in AmEx's good books you will always have that option to go for another card and further improve your average account age... you can do it next year, or the year after, or something - unless they change how they report to the CRAs, that will be an option you always have with them. No need to go freaking them out right away with a third application - they are easily spooked right now! That CL you got on the Delta is fantastic, it would be a shame to have them cut it to $500 or close the cards because they think you're behaving oddly or something - they would have to wonder why you want quite so many cards all in one day, and although WE know why... it may look strange and suspicious to them (not to mention that "in order to manipulate the info on my credit reports, that's why!" may not overly please them!)... so yeah, I'd hold off on that third app.
Congrats again, though! 
Me 5 Thanks for the advice, I think these two will help immeasurably. Not just the raw score but the manual reviews which would have previously made it clear my only personal credit cards were under a year old. So even if 'just' 20 points with the two new 22 year olds, it will make any serious LOC applications a lot easoier
Thanks for the advice, I think these two will help immeasurably. Not just the raw score but the manual reviews which would have previously made it clear my only personal credit cards were under a year old. So even if 'just' 20 points with the two new 22 year olds, it will make any serious LOC applications a lot easoier