It's not the temperatures that are the problem, it's where they're at. If you had a heat lamp and 4 inches down was at perfect temperature but the frogs were lets say 8 inches down, the frogs would not be getting heated right and this relates to what I'm getting at... the frogs are not above the substrate and so heat needs to be supplied from below or downwards, not side ways. I'm just saying as it this stage it is very important that frogs are kept at high temps and fed well in order to grow big healthy frogs that you will be able to breed. When it comes to the care of these frogs don't use the internet as your source, use books by breeders who have kept and bred the frogs for years with success