From what I've noticed, females are much less receptive to breeding after ovulation, so judging by how well she's pairing now it seems like she's still building and might just prefer to go later in the season than others. If the leopard is your top choice for a partner, you could try to toss him back in now - she might not have been ready for him in February.

While locks can last many hours, I think some males like to "hit it and quit it." Unless you see sperm plugs in the tub, it's probably safe to assume they got the job done. I don't have it on hand, but there's a video out there about how to tell if a male successfully locked by popping him and checking for the absence of a plug (if I remember correctly). Might be worth a look.

Congrats on your locks, hopefully she's just taking her sweet time and gives you a clutch that's worth the wait!