If the starters grew and looked healthy, they should have ripped thru that little wort in hours. Could it have finished overnight so you missed all activity, or the airlock leaked, and it is the hydro that is faulty? Seems like there would have been a krausen and a crud ring, though.
I just checked Mr. Malty's yeast calculator, and for 1.5 gal of 1.045 it said just 20% of one 11g dry yeast was sufficient, so clearly WAY more yeast than necessary was used. I don't know if such severe over-pitching can completely stall out and do absolutely nothing, i.e., not change the gravity at all.
Could it be possible that it chewed thru the sugars so quickly that it had no time to create a krausen or ring?
Just to be sure, Can you check your hydrometer to verify it's not broken? And taste the wort/beer to verify it's still sweet? At 1.045 it is a near-perfect sugar solution (1# sugar per 1 gallon water of 1.046.)
If it is not already beer, I can't imagine what would stop two active starters from doing that small job.
If it tastes sweet, and still clean (not souring, etc.) then maybe try a third dry or wet yeast with no starter. Half of a 5g package or one-third of a 11g package will suffice.
I've read that it is not necessary (even bad) to do a starter with dry yeast. The mfr prepares the yeast for storage, building up the glycogen and sterols in the yeast, so that all the yeast needs prior to pitching is proper H2O re-hydration. Dry yeast makers say making starter actually weakens the yeast by depleting those built-in energy reserves. Even so, you should have had plenty of yeast to process 1.5 gals of 1.045 (twice). But in the future, you can simply follow the mfr guidelines for re-hydrating 30 minutes before pitch time and avoid the pre-planning and work of a starter if you wish.
As I circled back thru this twisted and lengthy reply, I recall that I once had a problem with my starter gravities being too high, and I was essentially drowning my wet yeast in a high-sugar-then-alcohol bath, likely stunting them rather than boosting them. If the wort was severely over-pitched, then the starter was insanely over-pitched.
Is it possible that the yeast competed so fiercely for the limited food in the starter that they wiped themselves out? Depleted those reserves, starved, mutated and lost ability to process wort sugars?
Edit: found this Wyeast link on the effect of yeast pitch rates: http://www.wyeastlab.com/com-pitch-rates.cfm