I've had a sole Platy in my tank for about three months or so. Originally I had purchased three, but two died days after getting them. The only other fish in there are some zebra danios and a cory. I thought the one Platy was just getting fat until I noticed a few fry at the bottom of the tank. Everything I've read states the Platy should bear its young in 30-40 days. It's been more like 90 or so. Is this normal?